HomeMy WebLinkAboutCC AG PKT 2008-07-14 #R• AGENDA STAFF REPORT
DATE: July 14, 2008
TO: Honorable Mayor and City Council
THRU: David Carmany, City Manager
FROM: Lee Whittenberg, Director of Development Services
SUBJECT: RECEIVE AND FILE - INFORMATION ON "THE SHAKEOUT
EARTHQUAKE SCENARIO" AND THE "CALIFORNIA
EARTHQUAKE RUPTURE FORECAST"
SUMMARY OF REQUEST:
Receive and File Staff Report. Direct Staff to provide to the Planning Commission and
Environmental Quality Control Board for information and to return with additional
information and any recommended actions as appropriate.
• DISCUSSION:
Overview of "Shakeout Earthquake Scenario" Preparedness Exercise:
On November 13, 2008 City Staff will participate in the state -wide "Golden Guardian `08"
earthquake preparedness exercise. The purpose of this state -wide emergency response
exercise is to rest the ability of first responders to deal with the impact of a magnitude 7.8
earthquake on the San Andreas Fault in Southern California. The exercise is being jointly
organized by the Governor's Office of Emergency Services and the California Office of
Homeland Security.
"The planned emergency drill is underpinned by the most comprehensive analysis ever
of what a major Southern California earthquake would mean on the ground," said Dr.
Lucile Jones, chief scientist for U.S. Geological Surrey's Southern California Multi -
Hazards Demonstration Project. "We know this science will help state and local
agencies develop comprehensive emergency - response plans that will help us avoid the
worst impacts of a major quake."
• Agenda Item R
Z:\07 -14 -08 Council Meeting - Agenda Items\DS - Staff Report - R - Uniform Earthquake Forecast Report.doc\LIM06 -05 -08
Receive and File — Information on `The Shakeout Earthquake Scenario" •
and the `Califomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
Overview of "The Shakeout Earthquake Scenario":
In preparation for the Golden Guardian `OS' preparedness exercise a hypothetical
Scenario describing how a magnitude 7.8 earthquake on the San Andreas Fault in
Southern California, similar to the recent earthquake in China, would impact the region.
In the Scenario, the earthquake would:
❑ kill 1800 persons;
❑ injure 50,000 persons;
❑ cause $200 billion in damage; and
❑ have long- lasting social and economic consequences.
The Scenario outlines a hypothetical earthquake in which:
❑ The strongest shaking and greatest damage is near the stretch of the San
Andreas Fault that extends through the fastest growing areas of Southern
California, including the Coachella Valley, Inland Empire and Antelope Valley.
❑ At least 10 million people will be exposed to heavy shaking. California's efforts •
at mitigation have concentrated on life safety and have been largely successful.
Thus, in spite of the large numbers of people in highly shaken areas, deaths are
estimated at only 1,800.
❑ Building types known to be vulnerable to damage and collapse, do indeed
sustain major damage. All un- reinforced masonry buildings within 15 miles of
the San Andreas Fault are completely destroyed. Those that are not retrofitted
kill many occupants. Many other older building types without retrofitting
contribute to over $33 billion in damage to buildings.
❑ The fault offsets all lifelines crossing into Southern California at Cajon Pass
(Interstate 15), San Gorgonio Pass (Interstate 10) and along Route 14, including
pipelines, power lines, roads, railways, telecommunications and aqueducts.
❑ Strong shaking continues in downtown Los Angeles for 55 seconds - nearly 8
times longer than in the Northridge Earthquake
❑ The prolonged, strong shaking heavily damages and sometimes collapses
hundreds of old brick buildings, thousands of older commercial and industrial
concrete buildings, many wood -frame buildings, and even a few, high -rise steel
buildings. Over 600,000 buildings suffer at least some damage that causes tens
of thousands of injuries and hundreds of deaths, and leaves many thousands of
people without homes or jobs. •
DS - Staff Report - R - Uniform Earthquake Forecast Report 2
• Receive and File — Information on "The Shakeout Earthquake Scenario"
and the °Califomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
❑ Fire doubles the fatalities and economic losses. Around Southern
there will be 1,600 fires started large enough to warrant
fires merge into conflagrations that burn hundreds of city
Santa Ana winds, the models still indicate a further $65
and $22 billion in indirect losses fromithe fires.
a 911 call,
California,
and some
blocks. Assuming no
billion in direct losses
❑ Nearly two thirds of the hospital beds are non - functional in Los Angeles, Orange,
Riverside, and San Bernardino counties. At the same time, 50,000 people will
seek treatment at emergency rooms.
❑ Thanks to a $6 billion investment in seismic safety, the State highway system
fares well. However, although collapse is avoided, some bridges are non-
functional so that much of the highway is not passable on the day of the event.
The long duration of shaking takes a greater toll on bridges and overpasses
under the jurisdiction of cities and counties where the retrofitting processes are
not complete or have not begun.
❑ The largest long -term economic disruption comes from damage to the water
distribution system. Damage to this system will be so extensive that some areas
will have to replace the whole system, and some buildings will be without water
for as long as 6 months. The direct and indirect business interruption costs
attributed to the lack of water will be $50 billion.
❑ Most of the damage is predictable and much is preventable. Individuals can
protect themselves and help their community by:
❑ Storing more water than they already have
❑ Keeping a fire extinguisher and knowing how to use it.
❑ Securing their space. This means securing building contents from flying
around and reinforcing a building they own to the most current standards.
Provided as Attachment 1 for the information of the City Council and interested citizens
is the following documents regarding "The Shakeout Earthquake Scenario ":
❑ "Disaster Earthquake Scenario Unveiled for Southem California" web page,
http: / /usgs.gov /newsroom /article asp? ID =1947, downloaded June 4, 2008;
❑ "The Shakeout Earthquake Scenario — A Story That Southem Califomians Are
Wilting" web page, http: / /r)ubs.usgs.org /circ /l324, downloaded June 4, 2008;
❑ "The Shakeout Earthquake Scenario — A Story That Southem Califomians Are
Writing', U.S. Department of the Interior and U.S. Geological Survey, Circular 1324
and jointly published as California Geological Survey Special Report 207; and
Uniform Earthquake Forecast= Status Report 3
Receive and File — Information on °The Shakeout Earthquake Scenario" •
and the "Califomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
❑ "The Shakeout Scenario ", U.S. Department of the Interior, U.S. Geological Survey,
and California Geological Survey — USGS Open File Report 2008 -1150 and CGS
Preliminary Report 25, Version 1.0 — Table of Contents and Chapter 1: Executive
Summary. (Complete report available at the Department of Development Services
to review)
Overview of "Uniform California Earthquake Rupture Forecast":
The subject report was recently released by the U.S. Geological Survey, the California
Geological Survey, and the Southern California Earthquake Center and describes a new
earthquake rupture forecast for California developed by the 2007 Working Group on
California Earthquake Probabilities (WGCEP).
The study determines that the chances of having one or more magnitude 6.7 or larger
earthquakes in California over the next 30 years is greater than 99 %. Such quakes can
be deadly, as shown by the 1989 magnitude 6.9 Loma Prieta and the 1994 magnitude 6.7
Northridge earthquakes. The likelihood of at least one or more powerful quake of
magnitude 7.5 or greater in the next 30 years is 46% - such a quake is most likely to
occur in the southern half of the State. •
Provided as Attachment 2 for the information of the City Council and interested citizens
are the following documents:
❑ "Forecasting California's Earthquakes — What Can We Expect in the Next 30
Years?", USGS Fact Sheet 2008 -3027;
❑ "The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF)" web
page, http : / /r)ubs.usas.gov /of/2007/1437, downloaded April 15, 2008; and
❑ "The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF) ", dated
2008 - Contents, List of Appendices, and Executive Summary. (Complete report
available at the Department of Development Services to review)
FINANCIAL IMPACT:
None. Costs of staff preparation for and participation in the preparedness exercise are
ongoing administrative functions of the participating Departments.
Uniform Earthquake Forecest.CC Status Report 4
C7
C7
Receive and File — Information on "The Shakeout Earthquake Scenario"
and the "California Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
RECOMMENDATION:
Receive and File Staff Report. Direct Staff to provide to the Planning Commission and
Environmental Quality Control Board for information and to return with additional
information and any recommended actions as appropriate.
SUBMITTED BY:
NOTED AND APPROVED:
r
xe
Whittenberg, erector David Carmany
Development Services Depart ent City Manager
Attachments: (2)
Attachment 1: Documents regarding "The Shakeout Earthquake Scenario ":
❑ "Disaster Earthquake Scenario Unveiled for Southern
California" web page,
hftp://usgs.gov/newsroom/article.asr)?ID=1-947,,
downloaded June 4, 2008;
❑ "The Shakeout Earthquake Scenario — A Story That
Southern Californians Are Writing' web page,
http://pubs.us9s.org /circ11324, downloaded June 4,
2008;
❑ "The Shakeout Earthquake Scenario — A Story That
Southern Californians Are Writing', U.S. Department of
the Interior and U.S. Geological Survey, Circular 1324
and jointly published as California Geological Survey
Special Report 207; and
❑ "The Shakeout Scenario ", U.S. Department of the
Interior, U.S. Geological Survey, and California
Geological Survey — USGS Open File Report 2008-
1150 and CGS Preliminary Report 25, Version 1.0 —
Table of Contents and Chapter 1: Executive Summary.
(Complete report available at the Department of
Development Services to review)
Uniform Earthquake Forecast.CC Status Report 5
Receive and File — Information on °The Shakeout Earthquake Scenario" •
and the "Califomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
Attachment 2: Documents regarding the "Uniform California Earthquake
Rupture Forecast":
❑ "Forecasting California's Earthquakes — What Can We
Expect in the Next 30 Years? ", USGS Fact Sheet
2008 -3027;
❑ "The Uniform California Earthquake Rupture Forecast,
Version 2 (UCERF)" web page,
http : / /Dubs.usgs.4ov /of/2007/1437, downloaded April
15, 2008; and
❑ "The Uniform California Earthquake Rupture Forecast,
Version 2 (UCERF) ", dated 2008 - Contents, List of
Appendices, and Executive Summary. (Complete
report available at the Department of Development
Services to review)
0
Uniform Earthquake Forecast= Status Report 6
• Receive and File — Information on "The Shakeout Earthquake Scenario"
and the Tallfomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
ATTACHMENT 1
DOCUMENTS REGARDING THE SHAKEOUT
EARTHQUAKE SCENARIO":
❑ "DISASTER EARTHQUAKE SCENARIO UNVEILED
FOR SOUTHERN CALIFORNIA" WEB PAGE,
HTTP: // USGS .GOWNEWSROOM /ARTICLE.ASP ?ID =19
47, DOWNLOADED JUNE 4, 2008;
❑ "THE SHAKEOUT EARTHQUAKE SCENARIO - A
STORY THAT SOUTHERN CALIFORNIANS ARE
• WRITING" WEB PAGE,
HTTP: / /PUBS.USGS.ORG /CIRC /1324, DOWNLOADED
JUNE 4, 2008;
n
U
❑ "THE SHAKEOUT EARTHQUAKE SCENARIO - A
STORY THAT SOUTHERN CALIFORNIANS ARE
WRITING", U.S. DEPARTMENT OF THE INTERIOR AND
U.S. GEOLOGICAL SURVEY, CIRCULAR 1324 AND
JOINTLY PUBLISHED AS CALIFORNIA GEOLOGICAL
SURVEY SPECIAL REPORT 207; AND
❑ "THE SHAKEOUT SCENARIO ", USGS OPEN FILE
REPORT 2008 -1150 AND CGS PRELIMINARY REPORT
25, VERSION 1.0, U.S. DEPARTMENT OF THE
INTERIOR, U.S. GEOLOGICAL SURVEY, AND
CALIFORNIA GEOLOGICAL SURVEY - TABLE OF
CONTENTS AND CHAPTER 1: EXECUTIVE SUMMARY.
(COMPLETE REPORT AVAILABLE AT THE
DEPARTMENT OF DEVELOPMENT SERVICES TO
REVIEW)
Uniform Earthquake Forecast.CC Status Report 7
USGS Release: Disaster Earthquake Scenario Unveiled for Southern California (5/22/2008 10:00:00 AM)
aQUSGS
science for a Changing warlJ
- • ..
Disaster Earthquake Scenario Unveiled for Southern California
Released: 5/22/2008 10:00:00 AM
Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Clarice Nassif Ransom USGS
Phone: 703-648-4299
Jim Nickles. USGS
Phone: 916 - 278 -3016
Don Drysdale, CGS
Phone: 916-323-1886
Pagel of 3
Editors' notes: A telephone conference call is scheduled for 10:30 a.m. PDT for a brief presentation and opportunity for questions with the
principal authors. Call 605- 990 -0100, and enter conference code 1009678#
B -roll animations and high - resolution images are available at hU: / /urbanearth.usgs.gov /shakeout.
Scientists today unveiled a hypothetical Scenario describing how a magnitude 7.8 Southern California earthquake - similar to the recent earthquake
in China- would impact the region, causing loss of lives and massive damage to infrastructure, including critical transportation, power, and water
*MS.
In the Scenario, the earthquake would kill 1800 people, injure 50,000, cause $200 billion in damage, and have long - lasting social and economic
consequences. This is the most comprehensive analysis ever of what a major Southern California earthquake would mean, and is the scientific
framework for what will be the largest earthquake preparedness drill in California history, scheduled for November 13, 2008.
The November preparedness exercise, "Golden Guardian '08," will test the ability of emergency responders to deal with the impact of a magnitude
7.8 earthquake on the San Andreas Fault in Southem California, and is being jointly organized by the Governor's Office of Emergency Services
and the California Office of Homeland Security. The Golden Guardian exercise will occur during a week -long series of public events planned for
the "Great Southern California ShakeOut." A June 41' kick -off event is planned for the "Shakeout" to help communities plan to respond to the
risks highlighted in the Scenario.
The scientific report describing the ShakeOut Scenario, jointly published by the U.S. Geological Survey (USGS) and the Califomia Geological
Survey (CGS), will be released today during a Congressional hearing in Washington, D.C. The House Committee on Natural Resources,
Subcommittee on Energy and Mineral Resources, led by Chairman Jim Costa (D -CA), will hold an oversight hearing on USGS efforts to prepare
for future earthquakes, at 10:00 a.m. EDT in Room 1324, Longworth House Office Building
Although imaginary, the Shakeout Scenario is based on scientists' best predictions of what would actually occur during and after a major
earthquake on the San Andreas Fault.
The Scenario outlines a hypothetical earthquake in which:
• The strongest shaking and greatest damage is near the stretch of the San Andreas Fault that extends through the fastest growing areas of
Southern California, including the Coachella Valley, Inland Empire and Antelope Valley.
• At least 10 million people will be exposed to heavy shaking. California's efforts at mitigation have concentrated on life safety and have
•been largely successful. Thus, in spite of the large numbers of people in highly shaken areas, deaths are estimated at only 1,800.
Building types known to be vulnerable to damage and collapse, do indeed sustain major damage. All un- reinforced masonry buildings
within 15 miles of the San Andreas Fault are completely destroyed. Those that are not retrofitted kill many occupants. Many other older
building types without retrofitting contribute to over $33 billion in damage to buildings.
• The fault offsets all lifelines crossing into Southern California at Cajon Pass (Interstate 15), San Gorgonio Pass (Interstate 10) and along
Route 14, including pipelines, power lines, roads, railways, telecommunications and aqueducts.
• Strong shaking continues in downtown Los Angeles for 55 seconds - nearly 8 times longer than in the Northridge Earthquake
h4:// www. usgs.gov /newsroom/article.asp ?ID=1947 6/4/2001
USGS Release: Disaster Earthquake Scenario Unveiled for Southern California (5/22/2008 10:00:00 AM) Page 2 of 3
• The prolonged, strong shaking heavily damages and sometimes collapses hundreds of old brick buildings, thousands of older commercial
and industrial concrete buildings, many wood -frame buildings, and even a few, high -rise steel buildings. Over 600,000 buildings suffer at
least some damage that causes tens of thousands of injuries and hundreds of deaths, and leaves many thousands of people without homes of
jobs.
• Fire doubles the fatalities and economic losses. Around Southern California, there will be 1,600 fires started large enough to warrant
call, and some fires merge into conflagrations that bum hundreds of city blocks. Assuming no Santa Ana winds, the models still indic
further $65 billion in direct losses and $22 billion in indirect losses from the fires.
• Nearly two thirds of the hospital beds are non - functional in Los Angeles, Orange, Riverside, and San Bernardino counties. At the same
time, 50,000 people will seek treatment at emergency rooms.
• Thanks to a $6 billion investment in seismic safety, the State highway system fares well. However, although collapse is avoided, some
bridges are non - functional so that much of the highway is not passable on the day of the event. The long duration of shaking takes a greater
toll on bridges and overpasses under the jurisdiction of cities and counties where the retrofitting processes are not complete or have not
begun.
• The largest long -term economic disruption comes from damage to the water distribution system. Damage to this system will be so
extensive that some areas will have to replace the whole system, and some buildings will be without water for as long as 6 months. The
direct and indirect business interruption costs attributed to the lack of water will be $50 billion.
• Most of the damage is predictable and much is preventable. Individuals can protect themselves and help their community by:
- Storing more water than they already have
- Keeping a fire extinguisher and knowing how to use it.
- Securing their space. This means securing building contents from flying around and reinforcing a building they own to the most
current standards.
"The planned emergency drill is underpinned by the most comprehensive analysis ever of what a major Southern California earthquake would
mean on the ground," said Dr. Lucile Jones, chief scientist for U.S. Geological Survey's Southern California Multi- Hazards Demonstration Project.
"We know this science will help state and local agencies develop comprehensive emergency- response plans that will help us avoid the worst
impacts of a major quake."
The ShakeOut Scenario is the product of an interdisciplinary collaboration of over 300 scientists, engineers, and other experts from several
agencies, including the USGS, the California Geological Survey, Southern California Earthquake Center, California Office of Emergency Se*
and Seismic Safety Commission.
To create the Scenario, geologists determined the amount of potential motion on the part of the San Andreas Fault with the greatest risk of
imminent rupture, a 200 -mile long section from the Salton Sea in the Coachella Valley to just south of Gorman. From this, seismologists and
computer scientists modeled the ground shaking. Engineers and building professionals used the models of ground shaking to estimate damage to
the built environment. And from these damages, social scientists evaluated emergency response, casualties, and the impact on our economy and
society.
The following scientists and engineers led the development of individual sections of the ShakeOut Scenario. They were responsible for bringing
together the appropriate team of experts to analyze that aspect of the earthquake, leading the investigations and ensuring that the final document
was written. Each of them can speak to the goals of the Scenario, the main results and the details of their expertise. They can be reached by
contacting the USGS.
Dr. Lucy Jones, Seismologist, USGS, Chief Scientist
Dr. Kenneth Hudnut, Geologist, USGS, Geologic setting and ground motion prediction
Dr. Keith Porter. Engineer, University of Colorado, Physical Damages
Dr. Daniel Pond Geologist, USGS, Secondary Hazards
Ms. Hope Seligson, Engineer, MMI Engineering, HAZUS and loss estimation
Dr. Kimberley Shoaf, Public Health Scientist, UCLA School of Public Health, Mortality and morbidity •
Dr. Michael Reichle, Chief Seismologist (ret.), California Geological Survey, Lifelines Dr. Dennis S. Mileti, Sociologist, California Seismic
Safety Commission, Emergency Response
Dr. James oltz Social Psychologist, California Office of Emergency Services, Emergency Response Dr. Richard Bemknopf, Economist, USGS,
h":// www. usgs .gov /newsroom/article.aSD ?ID =1947 6i4i1)nnR
USGS Release: Disaster Earthquake Scenario Unveiled for Southern California (5/22/2008 10:00:00 A11O Page 3 of 3
Economics
Dr. Anne Wein, Decision Scientist, USGS, Economics
*Dale A. Cox, Project Manager, USGS
A copy of the full technical report, The Shakeout Scenario, is available online at http:// uo bs.usgs.gov /of/2008 /1150.
A non - technical summary narrative of the Scenario is online at ho: // ubs.usgs.gov /circ/1324/. Paper copies of the narrative are available by
request.
High resolution images, and a computer animation showing the earthquake rupture and its waves of energy spreading across Southern California
are online at http• / /urbaneart usgs gov /shakeout.
USGS provides science for a changing world. For more information, visit www.usgs.gov.
Subscribe to USGS News Releases via our electronic mailing list or RSS feed.
* * ** www.usgs.gov * * **
Links and contacts within this release are valid at the time of publication.
Department of the Interior I U.S. Geological Survey
URL: http: / /www.usgs.gov /newsroom /article.asp ?ID =1947
Page Contact Information: Ask USGS
Page Last Modified: 5/27/2008 9:44 :26 AM
•
http: / /www.usgs .gov /newsroom/article.asp ?ID =1947 6/4/200f
'he ShakeOut Earthquake Scenario - -A Story That Southern Californians Are Writing
Z'91E
thquake Hazards Program
3'repared in cooperation with the
:allfornia Geological Survey
J.S. Geological Survey Circular 1324
:alifornia Geological Survey Special Report 207
rersion 1.0
Pagel of 4
USGS Home
Contact USGS
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The ShakeOut Earthquake Scenario —A
Story That Southern Californians Are
Writing
3y Suzanne Perry, Dale Cox, Lucile )ones, Richard Bernknopf, James Goltz,
Kenneth Hudnut, Dennis Mileti, Daniel Pont!, Keith Porter, Michael Reichle,
Hope Seligson, Kimberley Shoaf, Jerry Treiman, and Anne Wein
68
0
'lttp: / /pubs.usgs.gov /circ /1324/ 6/4/2008
The ShakeOut Earthquake Scenario - -A Story That Southern Californians Are Writing
Page 2 of 4
•
Ground motion for the ShakeOut Scenario earthquake 60 seconds after the
southern San Andreas Fault first begins rupturing. Yellow shows the highest
amplitudes of ground motion. (Simulation by Rob Graves of URS Corporation
for the Southern California Earthquake Center on high- performance
computers at the University of Southern California; image courtesy of Geoff
Ely, University of California San Diego /San Diego Supercomputer Center.)
Introduction
The question is not if but when southern California will be hit by a major
earthquake —one so damaging that it will permanently change lives and
livelihoods in the region. How severe the changes will be depends on the
actions that individuals, schools, businesses, organizations, communities,
and governments take to get ready. To help prepare for this event, scientis
of the U.S. Geological Survey (USGS) have changed the way that earthquakW
scenarios are done, uniting a multidisciplinary team that spans an
unprecedented number of specialties. The team includes the California
Geological Survey, Southern California Earthquake Center, and nearly 200
sttp: / /pubs.usgs.gov /circ /1324/
f/4/')nnR
Che ShakeOut Earthquake Scenario - -A Story That Southern Californians Are Writing Page 3 of 4
3ther partners in government, academia, emergency response, and industry,
working to understand the long -term impacts of an enormous earthquake on
the complicated social and economic interactions that sustain southern
ifornia society. This project, the ShakeOut Scenario, has applied the best
rrent scientific understanding to identify what can be done now to avoid an
Earthquake catastrophe. More information on the science behind this project
will be available in The Shakeout Scenario (USGS Open -File Report 2008-
1150; http: / /pubs.usgs.ciov /of /2008/1150/).
The "what if ?" earthquake modeled in the ShakeOut Scenario is a magnitude
7.8 on the southern San Andreas Fault. Geologists selected the details of this
hypothetical earthquake by considering the amount of stored strain on that
part of the fault with the greatest risk of imminent rupture. From this,
seismologists and computer scientists modeled the ground shaking that
would occur in this earthquake. Engineers and other professionals used the
shaking to produce a realistic picture of this earthquake's damage to
buildings, roads, pipelines, and other infrastructure. From these damages,
social scientists projected casualties, emergency response, and the impact of
the, scenario earthquake on southern California &rwquo;s economy and
society. The earthquake, its damages, and resulting losses are one realistic
outcome, deliberately not a worst -case scenario, rather one worth preparing
F and mitigating against.
Decades of improving the life- safety requirements in building codes have
greatly reduced the risk of death in earthquakes, yet southern California's
aconomic and social systems are still vulnerable to large -scale disruptions.
Because of this, the ShakeOut Scenario earthquake would dramatically alter
the nature of the southern California community. Fortunately, steps can be
taken now that can change that outcome and repay any costs many times
aver. The Shakeout Scenario is the first public product of the USGS Multi -
Hazards Demonstration Project, created to show how hazards science can
increase a community's resiliency to natural disasters through improved
planning, mitigation, and response.
Download this report as a 24 -page PDF file (c1324.pdf; 15.7 MB).
For questions about the content of this report, contact Suzanne Perry
k1so of Interest
: wa avucil -rime rceoort luuS -1150 /CGS Preliminary Report 25 The Shakeout
scenario by Lucile M. Jones, Richard Bernknopf, Dale Cox, James Goltz,
(enneth Hudnut' Dennis Mileti, Suzanne Perry, Daniel Pont!, Keith Porter,
Hlchael Relchle, Hope Seligson, Kimberley Shoaf, Jerry Treiman, and Anne
.ttP: / /Pubs.usgs.gov /circ /i 324/ 6/4/2008
The ShakeOut Earthquake Scenario - -A Story That Southern Californians Are Writing
Wein
Page 4 of 4
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•
•
The ShakeOut Earthquake Scenario —A Story
That Southern Californians Are Writing
By Suzanne Perry, Dale Cox, Lucile Jones, Richard Bernknopf, James Goltz,
Kenneth Hudnut, Dennis Mileti, Daniel Ponti, Keith Porter, Michael Reichle,
Hope Seligson, Kimberley Shoaf, Jerry Treiman, and Anne Wain
Circular 1324
Jointly published as
California Geological Survey Special Report 207
• U.S. Department of the Interior
U.S. Geological Survey
U.S. Department of the Interior
DIRK KEMPTHORNE, Secretary
U.S. Geological Survey
Mark D. Myers, Director
State of California
ARNOLD SCHWARZENEGGER, Governor
The Resources Agency
MIKE CHRISMAN, Secretary for Resources
Department of Conservation
Bridgett Luther, Director
California Geological Survey
John G. Parrish, Ph.D., State Geologist
U.S. Geological , Survey, Reston Virginia: 2008 •
Y 9
This report and any updates to it are available online at httP://pubs.usgs.gov /circ /1324/
For product and ordering information: World Wide Web: http: / /www.usgs.gov /pubprDd/, Telephone: 1-886- ASK -USGS
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Cataloging -in- Publication data are on file with the Library of Congress (URL httpV/www.loc.govA.
Produced in the Western Region, Menlo Park, California
Manuscript approved for publication, April 21, 2008
Text edited by James W. Handley II and Peter Stauffer
Layout and design by Judy Weathers
FRONT COVER- -Ground motion for the Shakeout Scenario earthquake 60 seconds after the southern San Andreas Fault first begins rupturing. Yellow shows
the highest amplitudes of ground motion. (Simulation by Rob Graves of URS Corporation for the Southern California Earthquake Center on high - performance
computers at the University of Southern California; image courtesy of Geoff Ely, University of California San Diego /San Diego Supercomputer Center.)
BACK COVER —Within the ShakeOut Scenario study area are many neighborhoods like this one, at severe risk from fire following earthquake. Here, tightly •
packed wood buildings will enable small fires to spread and merge into conflagrations that can burn dozens of blocks. Fire following earthquake can have
devastating consequences, as tragically seen after the 1906 San Francisco, 1923 Tokyo, and 1995 Kobe earthquakes. It is a significant threat in urban areas
of California and doubles the fatalities and economic losses in the hypothetical ShakeOut earthquake. (Google Earth image.)
fffl
Contents
Introduction....................................................................................................................... ..............................1
The Shakeout Scenario Is Not a Prediction ............................................................... ..............................1
The ShakeOut Scenario Narrative ................................................................................ ..............................5
HowDo We Write the Ending? ..................................................................................... .............................15
AdditionalInformation .................................................................................................... .............................16
ShakeOut Scenario Coordinators:
Lucile Jones, USGS: Chief Scientist
Dale Cox, USGS: Project Manager
Suzanne Perry, USGS: Staff Scientist/Writer
Richard Bemknopf, USGS: Economics
James Goltz, Governors Office of Emergency Services: Emergency Response
• Kenneth Hudnut, USGS: Earthquake Design
Dennis Mileti, California Seismic Safety Commission: Emergency Response
Daniel Ponti, USGS: Secondary Hazards
Keith Porter, University of Colorado: Physical Damages
Michael Reichle, California Geological Survey: Lifelines Special Studies
Hope Seligson, MMI Engineering: HAZUS Loss Estimations
Kimberley Shoaf, University of California Los Angeles: Health, Safety, Social, Cultural, and Institutional
Jerry Treiman, California Geological Survey: Lifelines Special Studies
Anne Wain, USGS: Economics
•
•
•
The ShakeOut Earthquake Scenario —A Story That
Southern Californians Are Writing
BySuzanne Perry, Dale Cox, Lucile Jones, Richard Bernknopf, James Goltz, Kenneth Hudnut, Dennis Mileti,
Daniel Ponti, Keith Porter, Michael Reichle, Hope Seligson, Kimberley Shoaf, Jerry Treiman, and Anne Wein
Introduction
The question is not if but when southern
California will be hit by a major earthquake —
one so damaging that it will permanently change
lives and livelihoods in the region. How severe
the changes will be depends on the actions that
individuals, schools, businesses, organizations,
communities, and governments take to get ready.
To help prepare for this event, scientists of the
U.S. Geological Survey (USGS) have changed the
way that earthquake scenarios are done, uniting
a multidisciplinary team that spans an unprec-
edented number of specialties. The team includes
the California Geological Survey, Southern Cali-
fornia Earthquake Center, and nearly 200 other
partners in government, academia, emergency
response, and industry, working to understand the
long -term impacts of an enormous earthquake on
the complicated social and economic interactions
that sustain southern California society. This proj-
ect, the ShakeOut Scenario, has applied the best
current scientific understanding to identify what
can be done now to avoid an earthquake catastro-
phe. More information on the science behind this
project will be available in The ShakeOut Sce-
nario (USGS Open -File Report 2008 -1150;
http: / /pubs.usgs.gov /of /2008/1150/).
The "what if?" earthquake modeled in the
ShakeOut Scenario is a magnitude 7.8 on the
southern San Andreas Fault. Geologists selected
the details of this hypothetical earthquake by
considering the amount of stored strain on that
part of the fault with the greatest risk of immi-
nent rupture. From this, seismologists and com-
puter scientists modeled the ground shaking that
would occur in this earthquake. Engineers and
other professionals used the shaking to produce
a realistic picture of this earthquake's damage
to buildings, roads, pipelines, and other infra-
structure. From these damages, social scientists
projected casualties, emergency response, and the
impact of the scenario earthquake on southern
California's economy and society. The earth-
quake, its damages, and resulting losses are one
realistic outcome, deliberately not a worst -case
scenario, rather one worth preparing for and miti-
gating against.
Decades of improving the life -safety require-
ments in building codes have greatly reduced the
risk of death in earthquakes, yet southern Cali-
fornia's economic and social systems are still
vulnerable to large -scale disruptions. Because of
this, the ShakeOut Scenario earthquake would
dramatically alter the nature of the southern Cali-
fornia community. Fortunately, steps can be taken
now that can change that outcome and repay any
costs many times over. The ShakeOut Scenario
is the first public product of the USGS Multi-
Hazards Demonstration Project, created to show
how hazards science can increase a community's
resiliency to natural disasters through improved
planning, mitigation, and response.
The ShakeOut Scenario Is Not a
Prediction
On November 13, 2008, the ShakeOut Sce-
nario earthquake and projected damages will be
used as a basis for public drills and emergency
2 The ShakeOut Earthquake Scenario —A Story That Southern Californians Are Writing
response exercises, and so this hypothetical earth-
quake has been arbitrarily assigned a date, a time,
a plausible collection of aftershocks; and even
local weather conditions. Because it is a scenario
for planning, it provides detailed numbers, includ-
ing casualties, collapsed buildings, and business
losses. Yet, the Shakeout earthquake is not a
prediction. Certainly, a large earthquake involv-
ing this part of the San Andreas Fault is highly
probable. In fact, scientists have determined that
this is the most likely source of a large earthquake
in all of California (see Forecasting California's
Earthquakes —What Can We Expect in the Next
30 Years ?, U.S. Geological Survey Fact Sheet
2008 -3027; http : / /pubs - usgs.gov /fs/2008/3027/).
When the next San Andreas Fault earthquake
does happen, some things are inevitable —the
fault rupture will break any road, track, or pipe
..L
�i
s `
that crosses it, and intense shaking will damage
or destroy buildings that weren't constructed to
withstand it. The next earthquake will be differ-
ent in details from the ShakeOut earthquake, and
its total damages and losses will differ, because
each earthquake produces its own patterns of
shaking and damage. However, the widespread,
regional effects will be similar, and so will the
long -term social and economic impacts. Get-
ting prepared for the ShakeOut earthquake will
help southern Californians withstand other
earthquakes of comparable size. If we take no
additional actions for preparedness and mitiga-
tion, and the ShakeOut earthquake does occur,
it will cause some 2,000 deaths, 50,000 injuries,
$200 billion in damage, and severe, long- lasting
disruption. These numbers can climb with each
damaging aftershock.
„ ., `,�n..�.± y �y ^''.- "iy , ;}, -, . >: �Yr�a�t., v t,:� M:,�. .f•• \•
The Cajon Pass is one of five major' lifelinezarridors" that ate the veins and arteries. rough- hich', .
etaaa it life circulates in southern California: These iifeline camdors.allo .cdmmuters`, "gods;
telephone and Internet lines, electricity, water, ga.as,•nd fuelsro,rnove through tfie mountains that- ';• r, y2"
surround southem'Cali#aniia. Because mast of the corridors -must crassthe,southern San Andreas: ; ,. -,
Fault, future earthquakes are certain to severthe fifelines m one or more of these corridors and cause
sign ca' disruption bj� inferripting the•movemeni'of goods from the ports of tos.Angeles:- "-
and Long Beach.lUSGS photo 'bytucile Janes ►.'
: "Z7 .
.. , 1 e .v s.. v3 .. • n .. 6 _ r � , r'%:' r> .�T f r`'Yr i , s .. 'L` ' , \• �. 'l ` +x
%.. "ttIFELINES-CROSS;T.HE-FAULT
x''
..L
�i
s `
that crosses it, and intense shaking will damage
or destroy buildings that weren't constructed to
withstand it. The next earthquake will be differ-
ent in details from the ShakeOut earthquake, and
its total damages and losses will differ, because
each earthquake produces its own patterns of
shaking and damage. However, the widespread,
regional effects will be similar, and so will the
long -term social and economic impacts. Get-
ting prepared for the ShakeOut earthquake will
help southern Californians withstand other
earthquakes of comparable size. If we take no
additional actions for preparedness and mitiga-
tion, and the ShakeOut earthquake does occur,
it will cause some 2,000 deaths, 50,000 injuries,
$200 billion in damage, and severe, long- lasting
disruption. These numbers can climb with each
damaging aftershock.
„ ., `,�n..�.± y �y ^''.- "iy , ;}, -, . >: �Yr�a�t., v t,:� M:,�. .f•• \•
The Cajon Pass is one of five major' lifelinezarridors" that ate the veins and arteries. rough- hich', .
etaaa it life circulates in southern California: These iifeline camdors.allo .cdmmuters`, "gods;
telephone and Internet lines, electricity, water, ga.as,•nd fuelsro,rnove through tfie mountains that- ';• r, y2"
surround southem'Cali#aniia. Because mast of the corridors -must crassthe,southern San Andreas: ; ,. -,
Fault, future earthquakes are certain to severthe fifelines m one or more of these corridors and cause
sign ca' disruption bj� inferripting the•movemeni'of goods from the ports of tos.Angeles:- "-
and Long Beach.lUSGS photo 'bytucile Janes ►.'
: "Z7 .
.. , 1 e .v s.. v3 .. • n .. 6 _ r � , r'%:' r> .�T f r`'Yr i , s .. 'L` ' , \• �. 'l ` +x
THE EARTHQUAKE ADVANCES
0 :30 URS /USC o.os f_UU URS /USC o.os 1 2m& 2 :00 URS/USC oos " 2mlb
These computer - generated snapshots show ground motions for the Shakeout Scenario earthquake, in meters per second (m /s;1 fi%s is about 3.3 feet per second►, Yellow •
indicates higher amplitudes of ground motion. The snapshots show three points in tlm"O (left), 60 (center), and 120 (right) seconds after the sbutherh San Andreas Fault
(dashed white line) first begins rupturing at Bombay Beach, on the eastern shore of the Salton Sea. Note that soma areas remaKorangd ltolo fed for mdch longerthail others,
indicating extended, intense shaking in some of the sedimentary basins of southern California. (Simulation by Rob Graves of URS Corporation for the Southern' California Earthquake
Center on high - performance computers at the University of Southern California; images courtesy of Gobff Ely; University of Califorhia San Diego /Sah biego Superopinputer Canter.)
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•
•
The ShakeOut Scenario Narrative 5
The ShakeOutScenario Narrative
Much like a. movie script; the following fictional narrative will guide those participating in ;
the Shakeout Earthquake Scenario public drills and emergency response exercises on November,
13, 2008. More effectively than any statistics, this narrative describes what this magnitude 7:8
earthquake would be like in southern California if i10 additional actions are taken for mitigation
or preparedness.
Noveiniber' ' 13,:,2008
Thiirsda .9:50 a:rri� .. •1D minutes bef r•" �%�� ,4 begins..-
o •e a -quake J -
By°mid4io nin ybn this'workda` 200 000 commuters have made th i ,>
n9 y. a r- way•from�
kern; Riverside, and San Bernardino Counties into the Los Angeles area These driv- ; • , : _,
ers :trade it lengthy commute for the lower`cost'of housing in fast- growing communi-
ties like Victorville•und Lancaster, on thefar side of
the Sari Andreas'Fault. Others cross the fault in the
opposite direction, to employers in high desert com
munities: The commuters have joined 7.b mi Ilion, other = southera•Califor'nians,in workplaces constructed of
steel, concrete, brick, or wood. Of the marry millions of <= i
homes and workplaces, only a fraction are covered by'
earthquake insurance.
The life- safety provisions of California's building
codes have been improved over the years, and the
many fairly new homes in the Coachella Valley suf-
fer only minor damage., Yet every item inside these,
homes, if not secured, is heading to the floor. Shat-'
tered TVs and other home electronics create treach-
erous carpets of glass and cords.
Many older buildings suffer structural damage: Many
older concrete buildings quickly collapse,, trapping, occupants. The rupture front
continues its advance to San Gorgonio Pass and dismantles the ten miles of Inter- -
state 10 freeway that straddles the San Andreas Fault. The eastern part of River-
side County is now cut off from the iuestern part-, „
Thursday 90:01:00 a.m. 'Y .
Most people in Los Angeles and Ventura Counties are not yet aware of what is hap-
pening as the earthquake pounds the Coachella Valley and heads their way. By now
•
•
•
E
Tha ShakeOut Scenario Narraft's
the first waves have crashed through the Cajon Pass, severing the 115 freeway,
bending rail lines, and derailing a train. Roads, prev'iously through_qoing across the
fault, now end abruptly and pick up again 15 feet to fhe right.The strong shaking
also sends landslides across the rails and roads. '
Pipelinis snap and electrical trans-
mission lines fail. Spraying fuel ignites, causing an explosion.
Strong shaking begins to reverberate in the sediment -"
fi [led basins of the Inland Empire. Old warehouse , - - .,, -, '-
districts and historic downtowns are crumbling, and'
marry of their old, unretrofitted buildings have trapped
or killed the people inside. Many older concrete bulld-
ings ' have collapsed, and many older miao'dframe.buildirgs
have'shifted off their foundations, breaking qas.ino •
water lines'In the p I roCAM ..
The Coachella Valley is still sha"k'i n
Thursday 100 T.30 e, mi:
Over geologic +i-O the "I^+;^ 4C
11W , ri %. plates has
pushed the mountains of southern California up,•whili PENN I
fire, rain; and rivers have.brouglit the mountains down,
piece by Piece, filling 6asiris,with'sediments jand'ereating low, flat areas. Like many
cities, Los Angeles was built atop sedimenti. '56md'of the seismic waves now reach
these sediments and find easy territory in which to move back and forth, shaking
vigorously long after the waves fade elsewhere. Strong shaking aking will continue in Los
Angeles for 55 seconds, to the shock of residents who remember the strong shaking
during the 1994 Northridge earthquake, which lasted only 7 seconds.
T
I The ShakeOutEarthquake Scenario --A Story That Southero'Californians Are Writing
Thursday 10.02 a.m. (...2 minutes after the quake began...}
At last, the fault has stopped rupturing, bu +seismic;waves continue to advance
into Bakersfield, Oxnard, and Santa Barbara —here the shaking is just beginning.
Across southern California, the power is out. Emergency generators that have: D een
secured against earthquake shaking are still functional and now kick on.•The shaking',
has finati stop ed in the Caach tln VI-11 b t 44. e ' ft h
e ems- u a ors ocks are Just beginning.
Throughoutsoutherri Californialn the next feii•" >
months there -will be tens of thousands of ear #h
quake aftershocks large enough to feel. There will
be dozens lorge,enough to cause additional damage
,and•to imperil victims aridrescuers. Some of the .'
aftershock damage will be to people's psyches. Sig,
earthquakes are traumatic, and each new bout of
shaking increases stress, "especially! in" children who
are cut off from their families.
in the areas of strong shaking, many mobile homes ?'
`have collapsed off supports, snapping water, gas and
sewer lines, and blocking rescue routes. Mobile homes
installed snugly in shallow pits, or braced for earth -,
quakes, are still intact.
.The State highway system has fared well. A $6 bil- . "
lion investment in seismic retrofitting has paid off, ,
and the only highway deaths have been in crashes caused by intense earthquake'
shaking. However, the long duration of shaking has taken its toll on bridges and
overpasses within local jurisdictions, where the retrofitting process is not com-
pleted, or not yet begun.
No hospitals have seen complete collapses, but many hospital buildings are nonfunc
tional. Some hospital structures survived the shaking but must close due to nonstruc-
tural damage such as water pipes that break and f lood.
Thursday 10:05 a.m. (..: b minutes after the quake began,...)
The'U.S. Geological 5urvey'posts preliminary informa- ,
Lion about the earthquake. Learning that the magni- .
tude is 7.8, the world turns its attention to southern
California, Locally, news helicopters take to the.alr to
begin spot coverage of the devastation. With power
out, residents turn to their radios or talk to those they
meet in the streets, searching for any'information.
Across the region, phone systems, including
cellular and 911, are unusable, overwhelmed by the
vast number of attempted calls,
Thursday 10.30 a.m. (... 30 minutes after the
quake began...)
Emergency operations centers are activating,
and police, fire, and medical personnel shift into
•
•
The ShakeOut Scenario Narrative
emergency response mode, focusing on localized incidents with any means
available. They react quickly, according to their training and earthquake plans
established in advance.
All over the region, a foreseeable tragedy unfolds. Buildings that engineers knew were
going to perform badly, have performed badly. These are older buildings; constructed
with little earthquake resistance. The experts have names for them — non - ductile rein -
forced concrete, tilt-up concrete, unreinforced masonry,
soft-stories—and hundreds of these buildings have now -
followed their reputations into the dust. Thousands—of,
other •sftct4e` s are still.standing,but so gravely dam-
aged that they can never be, used again. '
While the earth still.shakes in plod s'Ia17` rom" the
earthquake's origin, people'in' the earliest;hit,areas
are beginning to •confront damaged buildings and to =
help those'who are trapped or hurt.:Lacking gloves,
crowbars, land training, some people claw through
debris with, bare hands. 'U'Ititnately, 95 percent of
those who are;•reicued will be.rescued by other
victims, as has •been seen in earthquake disasters
worldwide.
Air traffic is being diverted from southern California.
s
9 '
As people start to assess their situations, millions of them discover they are'
cut off from their families, with no way to learn the fate of their loved ones or
homes. This realization also hits first responders as they move out to help; they
understand that the disaster may seem to be over but is just beginning.
Fires are starting in countless ways. Power lines arc -, gas appliance lines snap...
chemicals spi Il and mix.- a lamp hits a sofa, unnoticed with the power out and the
earth shaking, then the power returns and the sofa starts to smolder... Most
of the fires start small, but not all are discovered right away. In any case, the
phones don't have dial tones. Even if they did, in a disaster this big and wide-
spread, there are not enough emergency personnel, to immediately respond to
every call for help. Worse, response is slowed by roads that are impassable due,
to damage, building debris, or abandoned cars. Worse still, in many places the. ,
water system is damaged, leaving inadequate water
pressure for fire fighting.
Once started, a small fire needs only minutes to
engulf a home or workplace. Around southern Califor -.
nia on this day, there will be 1,600 fires Iarge'enough
to warrant a 911 call. The stronger the shaking „the
greater, the number`of fires ignited. In areas With,
densely packed', wootdfrome buildings; some of• these
ignitions wild combine, spreading into conflagrations`
that burn dozens of blocks,
As soon as the shaking stops, ex'per'ts race to,
inspect dams around the •region: A few are found
to be' leaking at the toe- -a sign of potential fail =”
ure. Emergency responders are'spread even.,•
>
10 The Shakeout Earthquake .Scenario— A.Sio y That Sou&6rn- Californialns Are Writing
thinner when they must begin the evacuation of downstream areas. No dam
failures will occur in this particular earthquake.
Thursday 10:33 a.m. (... 33 minutes after the quake began...)
A magnitude 7.0 aftershock begins near the Salton 'Sea:and ruptures to the south.
Luckily, this is a relatively unpopulated area. Shak- ;
ing and its effects are felt throughout Imperial and
San Diego Counties, as well as in.Mexicah, Mexico. , ,
:.Damage to a darn'in San Diego`County requires ari ,
evacuation. Teaing of firefighters'from Sdn Diego - .
County �had;been.getting ready 'to'•come north to,help
with the initiaFearthquake's aftermath, but`are now
diverted to'respond to the strong aftershock affect
ing their;own county.
Thursday :12.00 noon (.. ,7 hours after the quake
began..) ;
Smaller fires are'merging into larger' fires in parts of
the •region where shaking was high and wood buildings.
are in close proximity. -World and national news cover-
age is focused on urban Los Angeles, especially on a
few collapsed buildings. This media focus makes the'
damage seem even worse than it is, and also more localized' . It will be several days
before a clear picture emerges of damage around the region.
Fire departments in Arizona and the San Francisco Bay area start to mobilize, but
mutual aid is hindered because so many roads into the.affected region are impass-
able. By now, some hospitals are beginning to receive and treat the injured, but
with routes and communications disrupted, ambulances struggle to reach victims'
and get them to hospitals.
November 14, 2008
Friday 03 :17 a.m. (... 17f hours after the quake began
A magnitude 7.2 aftershock begins near San Bernardino and ruptures west
along the base of the San Gabriel Mountains. This '
earthquake is considerably larger than 1994's .
magnitude 6.7 Northridge earthquake, which killed 33
people and cost more than $40 billion. The rupture"
stops 18 miles east of Pasadena, near Monrovia: The
location and size of this earthquake are devastating
to the already - weakened infrastructure and . .
overextended emergency response resources. The
aftershock triggers damaging aftershocks of its own.
Friday 0.7.00 a.m. (.__ 21 "hours after the quake
began..)
By now, a Presidential Disaster Declaration has been
issued, and Federal resources have been committed. -
The Federal Emergency Management Agency (FEMA),
the California Governor's Office of Emergency Services
•
•
The'ShakeOut Scenerio'Narrative 77
(OES), and Operational Areas for emergency manage6 4*have setup a Joint Incident- :
Command Center. Communications remain difficult-Ham radio operators begin to assist
official responders,
Ys
Since first hearing about-the earthquake, people outside southern California have
been trying to reach family and friends here. Very
few have succeeded.
Friday e9 :02 a.m. (.::23+ hours after ithe.quake
began...:. / =
A magnitude 5.6 aftershock rgtiiles residential areas Jn '
Ran& Cu6amonga.- his is a bit bigger than the 1990'
-Upland earthquake that caused more than $10 ,million in'
damage.
Friday'10.00 a.m. (....24 hours after the quake` `
began..:)
Utility companies are working around the clock to
restore services, yet most people in the areas;of
heaviest shaking'lack electricity, natural gas, and : E
water. Utility workers, like transportation crews, medical staff, and emergency
responders, push themselves to do their crucial jobs despite concerns about their
own families. "
Donations'of money, services, and material are arriv-
ing from all parts of the United States, and a few
Red Cross shelters have opened at public schools and
undamaged recreation centers, where food, water, ;
and personnel are available. Most people, particularly
in heavily damaged areas, are camped outside.
By now, most stranded motorists have been rescued, and
some families are at last,reuniting. To get around; emer-
gency responders are using helicopters and any other.
means of transportation that works, while residents are
using bicycles and four -wheel -drive vehicles.
November 15, 2008
• i
Saturday 11 :32 p.m. (... 2+ days after the quake began...)
A magnitude 5.7 aftershock occurs with an epicenter in Rialta. This is as large as the
1991 Sierra Madre earthquake that killed one person and caused $40 million in damage.
Fear of looting far exceeds the reality, yet by now many fearful rumors are cir-
culating. Despite official assurances to the contrary, concern grows that if dead
bodies are. not recovered and transported away, they will'cause disease outbreaks.
• Some are convinced that earthquake scientists are hiding knowledge that an even
bigger earthquake is imminent.
12 The ShakeOut Earthquake Scenari" Story That Southern Californian Are Writing
November 16, 2008 3 days after the quake began...)
It is getting easier for people outside southern California to make contact. • •'
with friends and family here. Urban search and rescue teams continue to make
rescues, but at a declining rate. Firefighters have
extinguished most of the major fires, except
where some conflagrations have merged into
super- conflagrations— monster fires that consume
everything for hundreds of blocks.
Many medical staff members have worked with=
out sleep since they first began responding to the ,
disaster Seriously damaged hospitals'have been;
evacuated, and open -air trauma centers have been '
set up •i n adjacent areas: 7T er a e :Is• .very short sup- E
ply of medical equipment su`cki as'kidney dialysis; ; A'
Mac' hines. 5ome,patients'are'being med- evacuated
outside the region, to hospitals in'Nevada,'Arizona,
and other parts of California Undamaged hospitals
have•an influx of earthquake victims with crush .
injuries, broken bones, and trauma. This increased ,
patient load is not distributed evenly, and some ;
undamaged hospitals are dramatically overloaded, while others receive few
patients.
By now, Red Cross shelters have been setup throughout the accessible parts of - r
the affected areas. The donation and distribution of money, services, and material
have intensified, yet unmet needs are widespread. A
coordinated effort among local, State, and Federal :.
government agencies is starting to bring water and,
food into the region, Our "just in time" economy does • �,;; ,$;, .•;;; ,x
not stockpile goods in warehouses.
,;
t' ''
QIUM ��:r•
The National Guard has been mobilized to handle spe=
cialized, earthquake- related law enforcement duties, .-
allowing local law enforcement to return to regular
duties. The fear of looting, intensified by media
emphasis, begins to abate. Police and.secilrity person-
nel maintain cordons around sites of building collapse,
but tenants and owners are allowed to reenter certain
other damaged buildings on a very limited basis,
1, 11111,1111111M W III
Mid- December, 2008 . <:
..Abouta month later...) .'
By now, most gas and electric services have been restored, even in the heavily damaged
areas closest to the San Andreas Fault, Landfills store millions of tons of fresh debris.
Most of the major roads have reopened, but they are Iiried with heaps of debris. Small
bridges that went down or remain damaged are keeping marry local roads dosed. Some
freeways also remain closed for repairs, where bridge retrofitting prevented collapse
but not all damage. Many commuters who work far from home are unable (and some are
�
The ShakeOut Scenario
By Lucile M. Jones, Richard Bernknopf, Dale Cox, James Goltz, Kenneth Hudnut, Dennis
Mileti, Suzanne Perry, Daniel Ponti, Keith Porter, Michael Reichle, Hope Seligson,
Kimberley Shoaf, Jerry Treiman, and Anne Wein
USGS Open File Report 2008 -1150
CGS Preliminary Report 25
Version 1.0
11:
U.S. Department of the Interior
U.S. Geological Survey
California Department of Conservation
(• California Geological Survey
U.S. Department of the Interior (•
DIRK KEMPTHORNE, Secretary
U.S. Geological Survey
Mark D. Myers, Director
State of California
ARNOLD SCHWARZENEGGER, Governor
The Resources Agency
MIKE CHRISMAN, Secretary for Resources
Department of Conservation
Bridgett Luther, Director
California Geological Survey
John G. Parrish, Ph.D., State Geologist
U.S. Geological Survey, Reston, Virginia 2008 (6
For product and ordering information:
World Wide Web: httpV /www.usgs.gov /pubprod
Telephone: 1-888-ASK-USG S
For more information on the USGS —the Federal source for science aboutthe Earth,
its natural and living resources, natural hazards, and the environment
World Wide Web: httpl/www.usgs.gov
Telephone: 1 -888- ASK -USGS
Suggested citation:
Jones, Lucile M., Bernknopf, Richard, Cox, Dale, Goltz, James, Hudnut, Kenneth, Mileti, Dennis,
Perry, Suzanne, Ponti, Daniel, Porter, Keith, Reichle, Michael, Seligson, Hope, Shoaf, Kimberley,
Treiman, Jerry, and Wain, Anne, 2008, The Shakeout Scenario: U.S. Geological Survey Open -
File Report 2008 -1150 and California Geological Survey Preliminary Report 25
[ http :/ /pubs.usgs.gov /of/2008/1150A.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply
endorsement by the U.S. Government
Although this report is in the public domain, permission must be secured from the individual •
copyright owners to reproduce any copyrighted material contained within this report
ii
•
The ShakeOut Scenario
By Lucile M. Jones', Richard Bernknopf , Dale Cox', James Goltz2, Kenneth Hudnut', Dennis
Mileti3, Suzanne Perry', Daniel Ponti', Keith Porte?, Michael Reichles, Hope Seligson,
Kimberley Shoaf, Jerry Treimans, and Anne Wein'
' USGS
2 Governor's Office of Emergency Services
'California Seismic Safety Commission
4 University of Colorado
'California Geological Survey
6 MMI Engineering
University of California, Los Angeles
USGS Open File Report 2008 -1150
CGS Preliminary Report 25
Version 1.0
2008
• U.S. Department of the Interior
U.S. Geological Survey
California Department of Conservation
California Geological Survey
iii
Contents 0
Chapter I. Executive Summary ............................................................. ..............................1
Chapter2. Introduction .............................................................. ............................... ....... 13
Chapter 3. Constructing the Scenario Event .......................... ............................... . ...25
Chapter 4. Physical Damages by Keith Porter ...................................... ..........................93
Chapter 5. Emergency Response and Communications by
Dennis Miled and James Goltz ................. ............................... ............................161
Chapter 6. Casualties by Kimberley Shoaf ........... ............................... ............................199
Chapter 7. Regional Economic Consequences by Anne Wein and Adam Rose .............209
Chapter8. Conclusions ......................................... ............................... ............................291
References............................................................. ............................... ............................295
V]
iv
•
The ShakeOut Scenario
CHAPTER 1. EXECUTIVE SUMMARY ................................................ ..............................2
Overview .. ................ .. ............ _ ... » ............ ... ............. .. ............ .. ............. .. ... .» ........ .. ..... ....» .....................
... ...
..... .....
... 2
Earth Science in the ShakeOut Scenario .. ........................... .. .................... .. ... .. ......... ...... ............ _. ..............................2
TheEarthquake Source ................................................................................. ............................... ..........2
........................
Ground Motions .............................................................................................................................. ............................... 3
FaultOffsets ............................................... ...............................
SecondaryHazards .......................................................................................................................... ............................... 5
Aftershocks..................................................................................................................................... ............................... 5
Engineering in the ShakeOut Scenario ..........................................................»............................... ............................... 6
Buildings......................................................................................................................................... ............................... 6
Non - structural and contents damage ................................... ............................... ,__.....7
..................... ...............................
Utilities, Lifelines, and Infrastructure .................. ............................... ... 7
......................................... ...............................
Fire Following Earthquake ................................................................ ............................... ........................ 8
...................
Social Science in the ShakeOut Scenario .............................. ............................... . g
• Emergency Services—. ..................................................................................................... ............................... ...�...
Mortality and Morbidity . ' 8
Business Interruption .......... ...............................
Movementof Goods .................................................................................................... ............................... ...........10
Conclusions ....... » ...........................................................................................................».................. .............................10
•
Chapter 1. Executive Summary
Overview
This is the initial publication of the results of a cooperative project to examine the
implications of a major earthquake in southern California. The study comprised eight counties:
Imperial, Kern, Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura. Its
results will be used as the basis of an emergency response and preparedness exercise, the Great
Southern California ShakeOut, and for this purpose we defined our earthquake as occurring at
10:00 a.m. on November 13, 2008. As members of the southern California community use the
Shakeout Scenario to plan and execute the exercise, we anticipate discussion and feedback. This
community input will be used to refine our assessment and will lead to a formal publication in early
2009.
Our goal in the ShakeOut Scenario is to identify the physical, social and economic
consequences of a major earthquake in southern California and in so doing, enable the users of our
results to identify what they can change now — before the earthquake —to avoid catastrophic impact
after the inevitable earthquake occurs. To do so, we had to determine the physical damages
(casualties and losses) caused by the earthquake and the impact of those damages on the region's
social and economic systems. To do this, we needed to know about the earthquake ground shaking
and fault rupture.' So we first constructed an earthquake, taking all available earthquake research
information, from trenching and exposed evidence of prehistoric earthquakes, to analysis of
instrumental recordings of large earthquakes and the latest theory in earthquake source physics. We
modeled a magnitude (M) 7.8 earthquake on the southern San Andreas Fault, a plausible event on
the fault most likely to produce a major earthquake. This information was then fed forward into the
Figure 1 -1. ShakeOut Scenario flow -chart.
Earth Science in the ShakeOut Scenario
The Earthquake Source
The ShakeOut Scenario earthquake is a magnitude 7.8 earthquake on the southernmost 300
km (200 mi) of the San Andreas Fault, between the Salton Sea and Lake Hughes. The southern San
Andreas Fault was identified in the most recent assessment of seismic risk as most likely source of
a very large earthquake in California. A magnitude 7.8 is not the largest earthquake that the
southern San Andreas Fault can produce, nor is the San Andreas the only fault to threaten the
populated areas of southern California with very large earthquakes. However, those other faults
have recurrence intervals (an estimate of the average time) between larger earthquakes that are
considerably longer, measured in thousands of years. By contrast, the southern San Andreas Fault
has generated earthquakes of ShakeOut size on average every 150 years —and on a portion of the
fault that ruptures in the ShakeOut Scenario, the last earthquake happened more than 300 years
0
•
A
• ago. The extent of the fault rupture in this earthquake was determined from geologic
characteristics, after considerable discussion among geologic experts. The most likely rupture
initiation point is one of the endpoints of the fault. We started at the southern end of the San
Andreas Fault, and ruptured the fault to the northwest. We assumed that the average amount of slip
to be released anywhere along the fault would be the amount accumulated since the last event on
that portion of the fault, ranging from 2 to 7 meters (6 to 23 ft). We then added a randomized
variation of the average slip within each 30 km section of fault. The maximum amount of slip is at
the southern end of the rupture near the Salton Sea, where it has been more than 300 years since the
last earthquake.
Ground Motions
The sudden rupture of a fault produces shaking as one of its effects. This shaking moves the
ground, and it is these ground motions that we feel and that cause most of the damage in an
earthquake. We estimated these ground motions with physics -based computer simulations of the
earthquake with computer systems developed by the Southern California Earthquake Center
information technology research program.
For the past 30 years, before recent advances in information technology that have enabled
scientists to obtain meaningful results from physics -based computer simulations, ground motion
predictions have typically been made using attenuation relations, which forecast the expected
shaking at a site from the magnitude and distance from the fault. However, in any earthquake there
are pockets of shaking that are considerably higher or lower because of other factors that affect
shaking, including site effects, directivity, and radiation pattern. Our physics -based simulations
• modeled all of these factors, primary and secondary, that affect ground shaking, using two inputs:
(1) the ShakeOut kinematic rupture description and (2) a velocity model that describes the seismic
characteristics of the southern California rocks through which the waves propagate. The results are
shown to be consistent with the newest attenuation relations from the Next Generation Attenuation
(NGA) relations.
We validated our modeling results through comparison of multiple methods, use of distinct
velocity models, and comparison with empirically based attenuation relations. In all, four teams
were engaged to make independent models of the ground motions. Several features of the
ShakeOut earthquake ground motions are consistent across all the models including:
• Very strong shaking (approaching 3 m/sec) near the fault;
• Strong shaking with medium to long durations (20 -45 sec) in the basins near the fault, including
the Coachella, San Bernardino, and Antelope Valleys;
• Damaging shaking (at least 0.5 m/sec) overlarge areas (10,000 kn?) of Los Angeles, San
Bernardino, and Riverside counties;
• Pockets of very strong shaking (>1.5 m/sec) with long durations (45 -60 sec) in areas of the San
Gabriel Valley and East Los Angeles.
Duration of strong shaking will be an important contributor to damage in any earthquake as
large as the ShakeOut Scenario earthquake. Shaking lasts a long time because it takes about 100
seconds for a fault this long to rupture and because some of the waves get trapped and reverberate
in sedimentary basins. In the ShakeOut Scenario earthquake (fig. 1 -2), the San Bernardino Valley
is shaken extremely strongly but for a relatively short duration, as are Wrightwood and Palmdale,
while the Coachella Valley has strong shaking with a long duration. Lower amplitude, but much
longer duration ground motions occur in the Los Angeles and Ventura sedimentary basins.
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Figure 1 -2. This "ShakeMap" is a representation of the shaking produced by the Shakeout Scenario
earthquake. The colors represent the Modified Mercalli Intensity with the warmer colors
representing areas of greater damage.
To estimate damages from Shakeout ground motion, the ShakeOut Scenario next calculated
ground motion parameters used by engineers to estimate damage to structures. Ground motion
parameters describe how the ground moves due to different measures of earthquake waves, and are
needed because different kinds of structures are damaged by different kinds of waves. The
ShakeOut Scenario created all the standard ground motion parameters: peak ground acceleration
(PGA), peak ground velocity (PGV), Modified Mercalli Intensity (MW, and spectral accelerations
at 0.3, 1.0, and 3 seconds.
Fault Offsets
Fault offsets occur where the fault that moves in the earthquake is exposed at the Earth's
surface. The ShakeOut fault rupture is on the San Andreas Fault and will be dominated by strike -
slip, or horizontal displacement, causing structures and lifelines that straddle the fault to be sheared
and offset as much as 9 meters (30 feet). Fortunately, there are few structures at risk of direct fault
damage from the ShakeOut earthquake, due to the rural setting of the southern San Andreas Fault
zone, and to the Alquist -Pdolo Earthquake Fault Zoning Act of 1972, which prevents the
construction of buildings used for human occupancy on the surface trace of active faults.
Damage from ShakeOut surface rupture is most serious where lifelines (roads, railroads,
and utilities) cross the fault. Many of these crossings are concentrated within a few mountain 10
4
• passes and the disruption to these lifeline corridors has a major economic impact. Roads cross the
fault at 966 places; the most critical damage occurs to Interstate 10 in the Coachella Valley and in
San Gorgonio Pass, Interstate 15 in Cajon Pass, CA -14, CA -111, CA -62, Box Canyon Road, and
Big Pines Highway. Other disrupted lifelines include fiber optic cables (90 crossings), petroleum
and natural gas pipelines (39 crossings), railroads (21 crossings), aqueducts (32 crossings), and
overhead electric power transmission lines (141 crossings).
Secondary Hazards
We investigated secondary hazards that can be triggered by large earthquakes in southern
California including liquefaction, landslides, tsunamis, and seiches. All of these have caused
significant additional damage in many big earthquakes, but only landslides and liquefaction will
produce significant impacts in the ShakeOut Scenario. The Shakeout Scenario earthquake will
produce between 10,000 and 100,000 individual landslides, the vast majority of which will consist
of rock falls, rock slides, rock avalanches, soil falls, disrupted soil slides and soil avalanches. Most
of these will occur on steep slopes within the Transverse Ranges, primarily in the eastern San
Gabriel Mountains. Conditions that can lead to liquefaction are potentially widespread in parts of
the eight - county area impacted by the ShakeOut Scenario earthquake, particularly the Santa Clara
River /Oxnard Plain areas of Ventura County, parts of the San Fernando and San Gabriel Valleys,
portions of the coastal basin or flatland areas of Los Angeles and Orange Counties, the Santa Ana
River corridor, the Imperial Valley, the southern Coachella Valley, and coastal areas of San Diego
County. However, liquefaction requires both strong shaking and a high ground -water table. Strong
ground motions from the ShakeOut Scenario earthquake mostly occur within the inland desert and
• mountain regions of southern California where ground water levels are typically low year - round.
As a result, only the southern Coachella Valley will suffer significant liquefaction impacts in the
ShakeOut Scenario earthquake, with localized liquefaction otherwise confined mostly to areas
adjacent to perennial stream and river channels, such as in the upper Santa Ana and Santa Clara
river basins. Because of the large distance from the earthquake to the coast, tsunamis are not a
significant risk.
Aftershocks
Aftershocks are earthquakes and cause shaking and damage just like any other earthquake.
Their additional shaking can damage weakened structures, necessitate evacuations, endanger rescue
workers, and undo efforts to restore and rebuild. Based on experience in numerous earthquakes
worldwide, after a mainshock earthquake as large as the ShakeOut Scenario earthquake, damaging
aftershocks can occur for decades in a broad region around southern California, and any given
region may experience more severe shaking from a close aftershock than from the original
mainshock. Aftershock behavior in the aggregate can be well described by some simple, empirical
laws, and these can be used to simulate sequences of aftershocks that realistically mimic actual
aftershock sequences. For the ShakeOut Scenario, we generated ten random realizations of
aftershocks for the first week following our mainshock. In reality, large, damaging aftershocks may
occur months or years after the initial event.
We picked one of the simulations to be the aftershocks for the ShakeOut drills. This
sequence includes two magnitude (M) 7 aftershocks. A M7.0 aftershock occurs 33 minutes after the
mainshock, beginning at the southern end of the mainshock, near the Salton Sea, and rupturing
south toward Mexico. It causes damage in Imperial and eastern San Diego Counties as well as in
• Mexicali, Mexico. A M7.2 event occurs 17 hours after mainshock on the Cucamonga Fault,
rupturing along the front of the San Gabriel Mountains from Cajon Pass to Monrovia. The
aftershocks in this sequence would cause substantial additional damage, but neither large
aftershock has been evaluated in detail.
Engineering in the ShakeOut Scenario
The damage and impacts of the ShakeOut Scenario earthquake were estimated through a
three -step process. First, FEMA's loss estimation program, HAWS, was run using the physics -
based ground motion model. For Los Angeles County, HAWS used a refined database of
structures created from tax assessor's data. For the other counties, this was not available and the
default HAWS database was used. In addition, HAZUS default mapping schemes (the
relationships between basic inventory data and the assumed structural characteristics) were
modified to reflect available information on unreinforced masonry buildings tabulated by the
California Seismic Safety Commission, building density concentrations in urban core areas, and
construction pattern changes over time throughout the eight counties. In the second step, expert
opinion was collected through 13 special studies and 6 expert panels. Panels generally estimated
impacts to public utilities, especially where multiple utility companies provide a public service
such as water supply or electricity. Engineers and operators were invited to attend the half -day
panel discussions, and were presented the results of prior Earth science studies (shaking, faulting,
etc.), as well as damage to other interacting lifelines that had already been assessed. They were
then asked to posit a realistic scenario of damage, service interruption, restoration, and to suggest
promising mitigation options. To complement the panels, special studies were used for buildings
and for lifelines when the panel process was impractical, such as private utilities or utilities (such
as highways) where in -depth analysis was desired. In these cases, contributors were selected for
their specialized expertise. They too were presented with all previously estimated Earth- science
and relevant utility impacts, and asked to summarize assets exposed to damage, evidence of past
seismic vulnerability, and to posit a realistic scenario of damage, loss of function, restoration, and
promising mitigation measures. Crucial special studies were reviewed by panels of highly qualified
experts. In the third step, the expert evaluations were merged with the HAZUS results to create the
final estimates of probable damages.
The major losses for this earthquake fall into four categories: building damages, non-
structural damages, damage to lifelines and infrastructure, and fire losses. Within each category,
the analysis found types of losses that are well understood —that have been seen in previous
earthquakes and the vulnerabilities recognized but not removed —and types of losses that had been
less obvious – where the type of failure is only recently understood or the extent of the problem not
yet fully recognized. The study also found numerous areas where mitigation conducted over the
last few decades by state agencies, utilities and private owners, has greatly reduced the
vulnerability. Because of these mitigation measures, the total financial impact of this earthquake is
estimated to be "only" about $200 billion with approximately 1,800 fatalities. However, these are
still big numbers
Buildings
Total losses to buildings are estimated at $33 billion. The two classes of older, known, poor
performers -- unreinforced masonry (where bricks or stone blocks with mortar form the bearing
walls, called "URM") and non - ductile reinforced concrete buildings - -pose the greatest risk to life
safety. These types of buildings are no longer allowed to be built, but many of these buildings still
exist and are not retrofitted. These types of buildings will be heavily damaged or destroyed near the
fault, but in general will suffer less damage in the Los Angeles area. All URM buildings in the City
of Los Angeles have been evaluated, and most have been strengthened to reduce loss of life. The
6
• strong shaking in Los Angeles will have very long periods (the waves will be big but slow) and
these smaller buildings will in many cases ride out the shaking with less damage.
Woodframe construction generally fares well in earthquake shaking and woodframe
buildings are less likely than other types of buildings to be damaged. However, because woodframe
construction is so prevalent in California, substantial losses will still occur. Woodframe building
damage is most likely:
• in older homes where the house is not bolted to the foundation or the cripple wall is not
reinforced.
• in buildings with a "soft first story" — a large opening such as garage door or display windows
on the first floor and without compensating reinforcement.
• in buildings where building codes were not rigorously followed - -a condition difficult to
recognized until after the earthquake.
Steel moment frame buildings built before 1994 were found to form cracks in their
connections during the 1994 Northridge earthquake. Similar damage occurred in the 1995 Kobe
earthquake and some buildings collapsed. Special study was conducted to analyze the behavior of
steel frame high -rise buildings in the ground motions modeled for this earthquake. This event
shows amplified long period motions caused by resonance in the sedimentary basins, particularly
the very deep Los Angeles Basin. A special panel of structural engineers evaluated the analytical
study and concluded "Given these ground motions, the collapse of some pre-1994 welded -steel
moment -frame buildings is a credible scenario." Because this result comes from the long period
• ground motions, the area where this type of damage is possible is relatively large and includes
much of the urbanized areas of Los Angeles, Orange, Riverside and San Bernardino Counties. It is
impossible to determine how many and which buildings are the most susceptible without detailed
structural analysis which is beyond the scope of this study. For the purposes of the ShakeOut
emergency drills, we posit that 5 steel moment -frame high -rise buildings will collapse and that 10
more will be "red- tagged."
Non - structural and contents damage
Non - structural and contents damage is damage to the parts of a building other than what is
holding it up, including interior walls, water pipes, air conditioning systems, and all moveable
property such as electronics, and dishes. As building codes improve and buildings remain standing
during earthquakes, the relative importance of non - structural damage increases. In recent
earthquakes, the non - structural and contents losses have typically been comparable to the structural
losses. Non - structural damages and mitigation have not been regulated in any way. Many of these
losses are simple to prevent through securing contents and non - structural elements of the buildings.
This is one of the most important ways that individuals can reduce the losses.
Utilities, Lifelines, and Infrastructure
California's investments in mitigation have paid off most obviously in increased robustness
and resiliency of the region's lifelines. The retrofitting of highway bridges, conversion of ceramic
insulators in the electric grid to polymers, and replacement of cast iron pipes mean that many
utilities will be able to restore function much more quickly after the earthquake.
Significant vulnerabilities remain in the water conveyance system and in the lifelines that
• cross the San Andreas Fault. Pipes of concrete and iron are brittle and break in many places in an
l
earthquake. The number of pipe breaks will be large enough that recreating the water system will
be necessary in the hardest hit areas. Because this earthquake affects such a large area, there will
not be enough pipe and connectors or trained manpower to repair all the breaks quickly. The worst
hit areas may not have water in the taps for 6 months. This damage to the water system will also
greatly increase the problems in fighting the fires that will follow the earthquake. The cost to repair
water and sewer lines will be $1 billion.
The lifelines that cross the fault will all break when the fault moves. This will disrupt the
movement of water, petroleum products, telecommunications, and general transportation. Repair of
the lifelines will be slowed because the lifelines all cross the fault at just a few passes in the
mountains and therefore interact with each other. For instance, repairing pipelines broken at Cajon
Pass will require access that depends upon repair to Interstate 15. That in turn could be delayed if a
wildfire starts after damage to the electric lines in the same location.
Many roads and highways will be impassable in the first few days after the earthquake
because of debris on the roads, damage to bridges, and lack of power for the traffic signals. This
will have a significant negative impact on the emergency response. Because of the major highway
bridge retrofit program of the last 20 years, highway bridges are not expected to completely
collapse, but some will not be passable. Many bridges on local roads have not been retrofitted and
more damage is expected on those. The continuing impairment of the roads for months after the
earthquake until everything can be repaired has a significant economic cost, estimated at $5 billion
over one year.
Fire Following Earthquake
Southern California is unfortunately well situated for major fires to be generated following •
earthquakes. The number of ignitions that will create fires large enough to call the fire department
can be extrapolated from previous earthquakes and depends upon the number of households at
different levels of seismic shaking. This leads to an estimate of 1,600 ignitions of which 1,200 will
be too large to be controlled by one fire engine company. In areas of dense woodframe
construction, these fires if not controlled will grew quickly to involve tens or hundreds of city
blocks. The fire risk is increased by the damage to the water distribution system and by the traffic
gridlock that will result from the Shakeout earthquake.
The final level of fire damage is difficult to assess because it depends upon several
unpredictable factors, especially the degree to which fires spread when the fire protection services
lose water and are overwhelmed. We use the minimum value from the fire estimates at $40 billion
in damage to buildings and $25 billion in damage to building contents.
Social Science in the ShakeOut Scenario
The ShakeOut Scenario earthquake causes damage to the built environment that then ripples
through and damages the social systems of the study region. This study has investigated the
impacts of the earthquake on emergency services, human health, the regional economy, and trade
operations from the Ports of Los Angeles and Long Beach.
Emergency Services
An emergency response matrix has been developed to help understand what the demands
for emergency services will be like. Seventeen functions of emergency services are grouped into
seven general classes of activities, including crisis information (public information and responder
communications), search and rescue, victim services (shelter, provision of food and water and the
• management and distribution of donated goods and services), access management and law
enforcement (control and security and traffic control), the staffing and functioning of emergency
operations centers, fire suppression, medical emergency response, and service restoration, (repair
of utilities, route recovery and debris removal). Research.results and experience in past earthquakes
have been analyzed to create this response matrix. Among the findings are that
95% of rescues from downed buildings are carried out by fellow victims. Training ordinary
citizens how to search safely could greatly reduce injuries.
• Many Emergency Operations Centers have not considered the impact of earthquakes on the
contents of their Centers. Securing computers and desks and other non - structural mitigation
activities would have large payoffs at low cost.
Mortality and Morbidity
Shaking in the ShakeOut Scenario earthquake will kill and injure many people, by causing
buildings to collapse, creating falling debris and flying objects, and increasing traffic accidents
when drivers lose control of automobiles. Many additional deaths and injuries will result in fires
that follow the shaking. Estimating the total number of injuries and deaths is very uncertain
particularly because the Scenario posits types of building failures that have not yet been observed.
Because of strong life- safety building codes over the years, the Shakeout Scenario estimates only
approximately 1,800 deaths, of which about half occur because of the fires following the
earthquake. There will also be about 750 people with very severe injuries who will require rapid,
advanced medical care to survive. Approximately 50,000 people will have injuries that need
emergency room care. The final mortality could increase if hospitals cannot function because of
• damage or if the transportation disruptions prevent people getting to emergency rooms.
Business Interruption
The economic impact of the earthquake is not limited to the structures and goods broken or
burnt in the event. Much of the economic activity of the southern California region will be
interrupted by the damage to structures and infrastructure. In particular, beyond their direct losses
in stock (such as buildings, machines, and inventory), businesses will be unable to function because
of loss of electricity, gas, water, and a transportation system. Some of the losses can be recaptured
when the business resumes but the amount recaptured decreases with time as customers and
suppliers find alternatives. Because the duration of outage is so long, the lack of water conveyance
becomes the largest factor in business interruption losses for the ShakeOut earthquake, resulting in
$50 billion in lost economic activity.
•
Northwest
Trade va ue: $3.213
JgtzL39,900
aae value: $52.0
Jobs: 1,114,700
Jobs:
Great Plains
Trade va 9.313Great Lakes
Jobs: 243,200 Trade value: $53.7B
j J _ bs: 681,800 ---A
Southeast I
tra Trade value: $37.
$32.513 Jobs: 498,900
700
ae value: $25.
Jobs: 275,300
Figure 1 -3. National Impact of San Pedro Ports. Source: BST Associates Trade Impact Report; 2007.
Movement of Goods
The Shakeout Scenario earthquake will be far enough from both Los Angeles International
Airport and the Ports of Los Angeles and Long Beach that the damage there will be minimal. This
of course is not the case for many other possible earthquakes. The availability of these
transportation resources is a significant asset in mobilizing the emergency response. Transportation
from the Ports to the rest of the country is carried predominately by rail lines which will be
rendered impassable by the fault offsets and ground motions. Significant economic disruption will
result and the extent of the damage depends critically on how rapidly the railways and highways
can be rebuilt.
The modeling estimates that the Ports will not function for the first 3 days after the event
because of lack of electricity, general chaos, and the potential for slight damage to large structures
such as cranes. For the next 2 weeks, the Ports will operate at 10% of capacity. because there will
be limited rail service and limited alternative transportation. They will gradually return to full
capacity from 2 weeks to 2 months as rail service is reestablished and highways reopen. We
estimate that 85% of the lost business will be recaptured but that 15% will be permanently lost to
ship diversions, perished products, cancelled Far East shipments, and declined bookings.
Conclusions
The magnitude 7.8 ShakeOut earthquake is modeled to cause about 1,800 deaths and $213
billion of economic losses. These numbers are as low as they are because of aggressive retrofitting
programs that have increased the seismic resistance of buildings, highways and lifelines, and
economic resiliency. These numbers are as large as they are because much more retrofitting could
still be done. The sources of the different losses are shown in Table 1 -1.
Table 1 -1. Total Regional Economic Impacts of Shake -Out (in billions of 2008 dollars).
10
�e
• Indicator
Total Impacts
Building Damage $32.7
Related Content Damage 10.6
High -Rise Building Damage 2.2
Related Content Damage 0.7
Fire Damage 40.0
Related Content Damage 25.0
Highway Damage 0.4
Pipeline (water, sewer, gas) Damage 1.1
Sub -total Property Damage 112.7
Business Interruption 96.2
Relocation Costs 0.1
Traffic Delay Costs 4.3
Sub -total Additional Costs 4.4
Total $213.3
The earthquake modeled here may never happen. Big earthquakes on the San Andreas Fault
are inevitable, and by geologic standards extremely common, but probably will not be exactly like
• this one. The next very damaging earthquake could easily be on another fault. However, lessons
learned from this particular event apply to many other events and could provide benefits in many
possible future disasters.
The ShakeOut Scenario has identified five major areas of loss:
• Older buildings built to earlier standards.
• Non - structural elements and building contents that are generally unregulated.
• Infrastructure crossing the San Andreas Fault.
• Business interruption from damaged infrastructure, especially water systems.
• Fire following the earthquake.
The ShakeOut Scenario also found that previous efforts to reduce losses through mitigation
before the event have been successful. There are dozens more actions and policies that could be
undertaken at the individual and community levels to further reduce these losses. For instance,
actions to improve the resiliency of our water delivery system would reduce the loss from business
interruption, as well as reduce the risk of catastrophic conflagrations. At an individual and business
level, actions to secure non - structural items in buildings and retrofitting of existing structures will
greatly reduce individual risk. Planning and preparedness can improve personal and business
resiliency.
Over the next 6 months, the ShakeOut Scenario will be used to prepare for future
earthquakes and exercise in the Great Southern California ShakeOut in November 2008. This
process will encourage public discussion of these risks and possible solutions. The risks can be
analyzed and described by scientists but the solutions will come from southern California itself.
I•
11
• Receive and File — Information on 'The Shakeout Earthquake Scenario"
and the °Califomia Earthquake Rupture Forecast"
City Council Staff Report
July 14, 2008
ATTACHMENT 2
DOCUMENTS REGARDING THE "UNIFORM CALIFORNIA
EARTHQUAKE RUPTURE FORECAST':
❑ "FORECASTING CALIFORNIA'S EARTHQUAKES -
WHAT CAN WE EXPECT IN THE NEXT 30 YEARS?",
USGS FACT SHEET 2008 -3027;
❑ "THE UNIFORM CALIFORNIA EARTHQUAKE
• RUPTURE FORECAST, VERSION 2 (UCERF)" WEB
PAGE, HTTP :HPUBS.USGS.GOV /OF/2007/1437,
DOWNLOADED APRIL 15, 2008; AND
•
❑ "THE UNIFORM CALIFORNIA EARTHQUAKE
RUPTURE FORECAST, VERSION 2 (UCERF)", DATED
2008 - CONTENTS, LIST OF APPENDICES, AND
EXECUTIVE SUMMARY. (COMPLETE REPORT
AVAILABLE AT THE DEPARTMENT OF
DEVELOPMENT SERVICES TO REVIEW)
Uniform Earthquake Forecast.CC Status Report $
•
Forecasting California's Earthquakes What Can We Expect
in the Next 30 Years?
In a naw comprehensive
scientists h ft deteftine'd that the
chance orhaving one or more piagnt
tude 6.7 brlarger earth#pakes in the
California area over Me'next 30 years is
greater than 99 %. Such quakes -can bey;K,
daedty; as shown by the7196fmagnitude
6.9 Loma Prieta and the 1994 negnituda� _`
671Uorthridge earthquakes. the like-
_...- =• - -- ,.
insurance, and i
will be affected
What Is an Earthquake
Rupture Forecast?
Californians know that their State is
subject to frequent —and sometimes very
destructive — earthquakes, Accurate forecasts
of the likelihood of quakes can help people
prepare for these inevitable events. Because
scientists cannot yet make precise predictions
of the date, time, and place of future quakes,
forecasts are in the form of the probabilities
that quakes of certain sizes will occur during
specified periods of time.
In our daily lives, we are used to making
decisions based on probabilities —from weather
forecasts (such as a 30% chance of rain) to
the annual chance of being killed by lightning
(about 0.0003%). Similarly, earthquake prob-
abilities derived by scientists can help us plan
and prepare for future quakes.
Earthquake forecasts for California have
been developed in the past by multidisciplinary
groups of scientists and engineers, each known
as a "Working Group on Califomia Earthquake
Probabilities" ( WGCEP 1988, 1990, 1995,
2003). However, tllose forecasts were limited
to particular regions of California Because
of this, WGCEP 2007 was commissioned to
develop an updated, statewide forecast, the
latest result of which is the Uniform California
U.S. Department of the Irwar
U.S. Geological Survey
Earthquake Rupture Forecast, Version 2, or
" UCERF" (U.S. Geological Survey (USGS)
Open -File Report 2007 -1437, http: //pubs.usgs.
gov/of/2007/14370. Organizations sponsoring
WGCEP 2007 include the USGS, California
Geological Survey, and the Southern California
Earthquake Center. The comprehensive new
forecast builds on previous studies and also
incorporates abundant new data and improved
scientific understanding of earthquakes.
When an earthquake occurs, two things
happen —a fault ruptures (a crack in the Earth's
crust gives way and slips under tectonic pres-
sure) and seismic waves, caused by this sudden
fault motion, radiate out like ripples from a
pebble tossed into a pond. The shaking that
occurs as seismic waves pass by causes most
quake damage. The strength of the waves
depends party on the quake's magnitude,
which is a function of the size of the fault that
moves and the amount of slip.
The UCERF study's goal was to determine
probabilities for different parts of California
of earthquake ruptures of various magnitudes,
but not to estimate the likelihood of shaking
("seismic hazard ") that will be caused by these
quakes. This distinction is important, because
even areas in the State with a low probability of
fault rupture can experience shaking and dam-
age from distant, powerful quakes.
USGS Fact Sheet 2008.3027
2008
California sits on the boundary between two of the Earth's major tectonic plates —the Pacific and North
American Plates —which move inexorably past each other at a rate of about 2 inches per year. Much of this
motion is accommodated from time to time by sudden slip on faults, producing earthquakes. Although the
San Andreas Fault is the main locus of slip, hundreds, if not thousands, of other faults splay out from the
plate boundary, spreading the threat of large earthquake ruptures through most of the State.
T he new Uniform California Earthquake Rupture Forecast ( UCERF) combines
information from geodesy (precise data on the slow relative movement of
the Earth's tectonic plates), geology (mapped locations of faults and docu-
mented offsets on them), seismology (occurrence patterns of past earth-
quakes), and paleossismology (data from trenches across faults documenting
the dates and offsets of past earthquakes on them). The firstthree kinds of data
are shown here as layers in the diagram. All four kinds of data are combined
mathematically to produce the final probability values for future ruptures in the
California area, in regions of the State, and on individual faults.
Building on several previous studies and decades of data collection, UCERF
was developed by a multidisciplinary group of scientists and engineers, known
as the 2007 Working Group on California Earthquake Probabilities. Advice and
commentwas sought regularly from the broader community of earthquake sci-
entists and engineers through open meetings and workshops. Where experts
disagreed on aspects of the forecast, alternative options were accounted for in
calculations to reflect these uncertainties. The final forecast is a sophisticated
integration of scientific fact and expert opinion.
Seismograph
C
Geologic field mapping and aerial
photos trace out California's many faults
and documentthe accumulated slip in earth-
quakes over thousands of years. Color spectrum
shows rates of slip, from fast (purple and red) to ve
slow (dark blue).
TECTONIC MOVEMENT
N -I
a to
Global positioning system (GPS)
observations by satellite document how fast
various points in California are moving (arrows) in —response to the steady motion of the Pacific and North
FAULTS
,
•
0.01% 0.1% 1%
-0
The final forecast results from
evaluating and integrating several
types of scientific data.
Trenching across the
Hayward Fault in Fremont
is
How Likely is a Damaging
Quake in the Next 30 Years?
California straddles the boundary between
two of the Earth's tectonic plates —as a result,
it is broken by numerous earthquake faults.
Taking into account the earthquake histories and
relative rates of motion on these many faults,
the UCERF study concludes that there is a
probability of more than 99% that in the next 30
years Californians will experience one or more
magnitude 6.7 or greater quakes, potentially
capable of causing extensive damage and loss
of life. For powerful quakes of magnitude 7.5
or greater, there is a 46% chance of one or more
in the next 30 years --such a quake is twice as
likely to occur (37%) in the southern half of the
State than in the northern half (15%).
Smaller magnitude earthquakes are more
frequent than larger quakes. According to the
new forecast, about 3 magnitude 5 or greater
quakes will occur in the California region per
year, and a magnitude 6 or greater quake about
every 1.5 years. These numbers do not include
aftershocks that follow larger quakes urclud-
ing them would roughly double the expected
number of magnitude 5 or greater quakes.
�TEWIDE F IU PRO 1
The numbers Fepresent curreht best estimates.
As earthquake science progresses, flies- prob- ,
abilities iiiill change: ,Actual repeat•times'v, J
considefably and only rarely will be exactly as
listed io the table. „
30 -year probability of "Average-
" Magnitude one or more events' * repeat .
greateitlianoe4quai ' ?`.time ;
to the magnitude (jrearsl;"- .
-7 •X 94%. • ;
'7.5
'•w
8 ,R , • ,14%
*Not including Cascadia Subduc#6n Zane ,, r
For the entire California region, the fault
with the highest probability of generating at
least one magnitude 6.7 or larger earthquake is
the southern San Andreas (59% in the next 30
years). For northern California, the most likely
source of such a quake is the Hayward- Rodgers
Creek Fault (31 % in next 30 years) --see
USGS Fact Sheet 2008 -3019. Quake probabili-
ties for many parts of the State are similar to
those in previous studies, but the new probabil-
ities for the Elsinore and San Jacinto Faults in
southern California are about half those previ-
ously determined. For the far northwestern part
of the State, a major source of quakes is the
offshore 750- milelong "Cascadia Subduction
Zone," which extends south about 150 miles
into California. For the next 30 years there is
a 10% probability of a magnitude 8 to 9 quake
somewhere along the zone --such quakes occur
about every 500 years.
® Printed on recycled paper
_. Which Faults Currently Have Elevated Probabilities?
The new California earthquake forecast incorporates the con-
"• cept that earthquake probabilities change with time. For exam-
pie, a large quake may be less likely in the near future on a fault
that has recently had on"ut more likely on a fault on which
r. # the tectonic stresses have had much time to build back up. The
^?:fVorthem San Andreas} ault forecast also incorporates adjustments for areas that have
recently shown a change in the level of earthquake activity"
Faults that have elevated current probabilities include the south-
'; ern San Andreas and Hayward - Rodgers Creek Faults, though
Hayward - Rodgers major quakes on these faults may still be decades away.
Creek Fault
Calaveras Fa Current Earthquake Probabilities
=� Relative to Long -Term Probabilities
i� 1.6times Equal 1.6times
Garlock Fault
smaller greater
'A
\".
Southern San Andreas Fault
San Jacinto Fault
Elsinore Fault
a 200 MILES,
f 1
0 200 KILOMErERS
The UCERF forecast was evaluated by an
independent scientific review panel, as well as
by both the California and National Earth-
quake Prediction Evaluation Councils, making
it one of the most extensively reviewed earth-
quake forecasts ever produced. Uncertainties
remain because the new quake probabilities
are the result of evaluating and accommodat-
ing several earthquake theories. As scientific
understanding of quakes improves, the prob-
abilities will change.
The results of the UCERF study are a
reminder that all Californians live in earthquake
country and should therefore be prepared (see
Putting Down Roots in Earthquake Country at
httpJ /www carthquakccountry .info/roots). The
Ndivi UAL
The, I TIE
The• UCERF repdrt` assigns individual probabili=•,
x ties to 'specific known major faults: B -low ere:;
30 -year probabilities for seven of the faults for'
which scientists,have.the most data. Many other
„faults also'have'significent probabilitie"n fact•
the next big,quake in Califomia is just as likely,t4_ "
occur or one of thdotherfaults iq the State: ;
ProSabilityof ooe or-
I more magnitude.6.7;
^c or greater quake
Soiitherii San Andreas 59966
' Iiayvvard- Rodgers6reajc 31%
I ski Jac htt '
�Ttiitliein S�ati,Andreas • 219G,
Efsiiibie Tw ::i 11 %. kV
`Gar1Qi is 696'.
USGS has already used the UCERF to estimate
California's seismic hazard, which in turn
will be used to update building codes. Other
subsequent studies will add information on the
vulnerability of manmade structures to estimate
expected losses ("seismic risk"). In these ways,
UCERF will help to increase public safety and
community resilience to earthquake hazards.
Earthquakes cannot be prevented, but the
damage they do can be greatly reduced through
prudent planning and preparedness. The ongo-
ing work of USGS, California Geological
Survey, Southern California Earthquake Center,
and other scientists in evaluating quake prob-
abilities is part of the National Earthquake Haz-
ard Reduction Program's efforts to safeguard
lives and property from the future quakes that
are certain to strike in California and elsewhere:
in our Nation.
Edward H. Flelit Kevin R. Milner,
and the 2007 Working Group on
California Earthquake Probabilities
Edited by Peter H. Shaeffer and lames W. Hendley H
lbw by David R. ]ones
COOPERATING ORGANIZATIONS
Southern California Earthquake Center (SCEC)
California Geological Survey (CGS)
California Earthquake Authority
For more information contact
Earthquake Information Hotline (650) 3294085
U.S. Geological Survey, Mail Stop 977
345 Middlefield Road, Menlo Park, CA 94025
htW.11 atthquake.- SLgov/
http: //www.scec.org
This Fact Sheet and any updates to it are available
online at httpJ/pubs.usp.gov /f&i=8no27/
•
.he Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)
Prepared in cooperation with the
'"alifornia Geological Survey
and the
Southern California Earthquake Center
JSGS Open File Report 2007 -1437
:GS Special Report 203
XEC Contribution #1138
Pagel of 3
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The Uniform California Earthquake Rupture
Forecast, Version 2 (UCERIF 2)
By 2007 Working Group on California Earthquake Probabilities*
2008
and H. Field, Timothy E. Dawson, Karen R. Felzer, Arthur D. Frankel, Vipin Gupta, Thomas H. Jordan, Tom
sons, Mark D. Petersen, Ross S. Stein, Ray J. Weldon II, and Chris J. Wills
Predicted fte of Ell t 6.5 Ratb of Preftbd Rata of M t 6.5 to
Extrapolated Rats ft m W5
ar•o►probabaar ayNrpmbaunyr
I N milli: 11111111 Is 0111111 .1111, ;'1'111111;, nNa
1.6m 0.001% tkim
0.t Q9 ?,0 32 6p
itlp:/ /pubs.usgs.gov /of/2007/1437/ 4/15/2008
The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)
Page 2 of 3
California's 35 million people live among some of the most active earthquake faults in the United States. Public
safety demands credible assessments of the earthquake hazard to maintain appropriate building codes for safe
construction and earthquake insurance for loss protection. Seismic hazard analysis begins with an earthquake
rupture forecast —a model of probabilities that earthquakes of specified magnitudes, locations, and faulting type
will occur during a specified time interval. This report describes a new earthquake rupture forecast for California
developed by the 2007 Working Group on California Earthquake Probabilities (WGCEP 2007).
Main Text
Download the main text of this 104 -page report (of2007- 1437_text.pdf; 11.5 MB).
Download iust the Executive Summary as a 7 -page report (of2007- 1437_summary.pdf; 0.7 MB).
Download a supplemental Excel workbook. This workbook contains supplementary materials in 13 spreadsheets
(of2007- 1437_data.xis; 0.3 MB):
• Sheet (1) Rupture Magnitudes & Rates
• Sheet 2: Total 30 -year Rupture Probabilities
• Sheet 3: Total 5 -year Rupture Probabilities
• Sheet 4: M >_6.7 30 -year Rupture Probabilities
• Sheet 5: Segment Rates & Mean Recurrence Intervals
• Sheet 6: Total 30 -year Segment Probabilities
• Sheet 7: Total 5 -year Segment Probabilities
• Sheet 8: M>_6.7 30 -year Segment Probabilities
• Sheet 9: M>_6.7 Probabilities in WGCEP (2003: Box
• Sheet 10: Total 30 -year Probabilities on Faults
• Sheet 11: M>_6.7 30 -year Probabilities on Faults
• Sheet 12: B -Fault Data
• Sheet 13: Region Polygons
lkppendixes
appendix A: California Fault Parameters for the National Seismic Hazard Maps and Working Group on California
arthquake Probabilities 2007, by C.J. Wills, R.J. Weldon II, and W.A. Bryant
kppendix B: Recurrence Interval and Event Age Data for Type A Faults, by T.E. Dawson, R.J. Weldon II, and G.P.
3iasi
kppendix C: Monte Carlo Method for Determining Earthquake Recurrence Parameters from Short Paleoseismic
:atalogs: Example Calculations for California, by T. Parsons
kppendix D: Magnitude -Area Relationships, by R.S. Stein
•
kppendix E: Overview of the Southern San Andreas Fault Model, by R.J. Weldon II, G.P. Biasi, C.J. Wills, and T.E.
)awson
kppendix F: Summary of Geologic Data and Developments of A- Priori Rupture Models for the Elsinore, San Jacinto,
ind Garlock Faults, by T.E. Dawson, T.K. Rockwell, R.J. Weldon II, and C.J. Wills
kppendix G: Development of Final A -Fault Rupture Models for WGCEP /NSHMP Earthquake Rate Model 2.3, by E.
7eld, R.J. Weldon II, V. Gupta, T. Parsons, W.J. Wills, T.E. Dawson, R.S. Stein, and M.D. Petersen
tppendix H: WGCEP Historical California Earthquake Catalog, by K.R. Felzer and T. Cao
ttp : / /pubs.usgs.gov /of/2007/1437/ an SmnnQ
The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)
Appendix I: Calculating California Seismicity Rates, by K.R. Felzer
Page 3 of ?
Appendix J: Spatial Seismicity Rates and Maximum Magnitudes for Background, by M.D. Petersen, C.S. Mueller,
61 Frankel, and Y. Zeng
Appendix K: A- Priori Rupture Models for Northern California Type -A Faults, by C.J. Wills, R.J. Weldon II, and E.H.
Field
Appendix L: Cascadia Subduction Zone, by A.D. Frankel and M.D. Petersen
Appendix M: Empirical Estimation of Regional Time Variation in Seismicity, by K.R. Felzer
Appendix N: Conditional, Time - Dependent Probabilities for Segmented Type -A Faults in the WGCEP UCERF 2, by
E. H. Field and V. Gupta
Appendix O: Paleoseismic Investigations of the Walnut Site on the San Jacinto Fault, by T.E. Fuma/ and K.J.
Kendrick (three large sheets)
Appendix P: Compilation of Surface Creep on California Faults and Comparison of WGCEP 2007 Deformation Model
to Pacific -North America Plate Motion, by B.A. Wisely, D.A. Schmidt, and R.J. Weldon II
For questions about the content of this report, contact William Ellsworth
Suggested citation and version history
Iwo of Interest
USGS Fact Sheet 2008 -3027 Forecasting California's Earthquakes —What Can We Expect in the Next 30 Years? by
Edward H. Field, Kevin R. Milner, and the 2007 Working Group on California Earthquake Probabilities
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1W ence>hiia Than- - ra�rid
The Uniform California Earthquake Rupture
Forecast, Version 2 (UCERF 2)
By 2007 Working Group on California Earthquake Probabilities*
USGS Open File Report 2007 -1437
CGS Special Report 203
• SCEC Contribution #1138
2008
*Edward H. Field, Timothy E. Dawson, Karen R. Felker, Arthur D. Frankel, Vipin Gupta,
Thomas H. Jordan, Tom Parsons, Mark D. Petersen, Ross S. Stein, Ray J. Weldon II, and
Chris J. Wills
U.S. Department of the Interior
U.S. Geological Survey
• California Department of Conservation
California Geological Survey
U.S. Department of the Interior
DIRK KEMPTHORNE, Secretary
U.S. Geological Survey
Mark D. Myers, Director
State of California
ARNOLD SCHWARZENEGGER, Governor
The Resources Agency
MIKE CHRISMAN, Secretary for Resources
Department of Conservation
Bridgett Luther, Director
California Geological Survey
John G. Parrish, Ph.-D., State Geologist
U.S. Geological Survey, Reston, Virginia 2008
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Suggested citation:
2007 Working Group on California Earthquake Probabilities, 2008, The Uniform California
Earthquake Rupture Forecast, Version 2 (UCERF 2): U.S. Geological Survey Open -File Report
2007 -1437 and California Geological Survey Special Report 203
[ http : / /pubs.usgs.gov /of/2007/1091h.
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•
Executive Committee (ExCom)
Edward A. Field (Chair)
Tom Parsons
Mark D. Petersen
Ross S. Stein
Ray J. Weldon II
Chris J. Wills
Scientific Review Panel (SRP)
William L. Ellsworth (Chair)
Michael L. Blanpied
Lloyd C. Cluff
C. Allin Cornell
Arthur D. Frankel
David D. Jackson
David P. Schwartz
Steve G. Wesnousky
U. S. Geological Survey, Pasadena, Calif:
U. S. Geological Survey, Menlo Park, Calif:
U. S. Geological Survey, Golden, Colo.
U. S. Geological Survey, Menlo Park, Calif:
SCEC, University of Oregon, Eugene, Oreg.
California Geological Survey
U. S. Geological Survey, Menlo Park, Calif.
U. S. Geological Survey, Reston, Virg.
Pacific Gas and Electric Company
Stanford University, Stanford, Calif.
U. S. Geological Survey, Golden, Colo.
University of California, Los Angeles, Los Angeles, Calif.
U. S. Geological Survey, Menlo Park, Calif:
University of Nevada, Reno, Reno, Nev.
Management Oversight Committee (MOC)
Thomas K Jordan (Chair) SCEC Director, University of southern Califomia
• Rufus D. Catchings U. S. Geological Survey, Menlo Park, Calif:
Jill R. McCarthy U. S. Geological Survey, Golden, Colo.
Michael S. Reichle California Geological Survey
-i
iii
Authors and Co-authors of Appendices
Glenn P. Biasi
William A. Bryant
Tianqing Cao
Timothy E. Dawson
Karen R. Felzer
Edward R Field
Arthur D. Frankel
Thomas E. Fumal
Vipin Gupta
Katherine J. Kendrick
Charles S. Mueller
Tom Parsons
Mark D. Petersen
David A. Schmidt
Ross S. Stein
Tom K. Rockwell
Ray J. Weldon 11 -
Chris J. Wills
Beth A Wisely
Yuehua Zeng
University of Nevada, Reno, Reno, Nov.
California Geological Survey
California Geological Survey
U. S. Geological Survey, Menlo Park, Calif
U. S. Geological Survey, Pasadena, Calif.
U. S. Geological Survey, Pasadena, Calif.
U. S. Geological Survey, Golden, Colo.
U. S. Geological Survey, Menlo Park, Calif
SCEG University of Southern California
U. S. Geological Survey, Pasadena, Calif
U. S. Geological Survey, Golden, Colo.
U. S. Geological Survey, Menlo Park, Calif.
U. S. Geological Survey, Golden, Colo.
University of Oregon, Eugene, Oreg.
U. S. Geological Survey, Menlo Park, Calif.
San Diego State University, San Diego, Calif.
•SCEC/University of Oregon, Eugene, Oreg.
California Geological Survey
University of Oregon, Eugene, Oreg.
U. S. Geological Survey, Golden, Colo.
iv
0
UCERF 2 Report
Contents
Listof Appendices ........................................................................................................ ............................... A
List of Supplementary Materials .. ............................... ..
ExecutiveSummary ........................................................................................................ ..............................1
A. Introduction ............................................................................................................... ............................... 9
A.1. Motivation and Structure of WGCEP ( 2007) ..................................................... .............................11
A.2. Key Differences and Updates from Previous WGCEP Models ......................... .............................12
A.3. Modeling Framework ......................................................................................... .............................13
A.4. Representation of Epistemic Uncertainty ........................................................... .............................14
A.S. Review and Consensus - Building Processes ....................................................... .............................16
A.6. Key Products ...................................................................................................... .............................18
A.7. Report Organization ........................................................................................... .............................19
B. Fault Models ............................................................................................................ ............................... 20
B.1. Fault Section Database ..................................................................................... ............................... 20
B.2. Alternative Fault Models .................................................................................. ............................... 22
C. Deformation Models ............................................................................................... ............................... 24
C.1. Preferred and Alternative Deformation Models ............................................... ............................... 24
C.2. Aseismic Slip Factors ....................................................................................... ............................... 27
C.3. Crustal Shear Zones ......................... ............................... . ...... ............................... 29
.........
C.4. Path - Integral Tests of Deformation Models ..... ............................... . 30
....... ...............................
D. Earthquake Rate Models..
.................................................................................................... .. 33
................
D.1. Earthquake Source Types ................................................................................. ............................... 33
• D.2. Reduction of Moment Rate on Faults ............................................................... ............................... 34
D.3. Type -A Source Rate Models ............................................................................ ............................... 35
DA. Type -B Source Rate Models ............................................................................ ............................... 41
D.S. Type -C Source Rate Models ............................................................................ ............................... 42
D.6. Background Seismicity Rate Models ............................................................... ............................... 43
D.7. The Cascadia Subduction Zone ........................................................................ ............................... 43
D. 8. Tests of the Earthquake Rate Models ............................................................... ............................... 46
E. Probability Models .................................................... ............................... ............ 59
... ...............................
E.1. WGCEP (2003) Probability Models ................................................................. ............................... 59
E.2. Selection of Probability Models ........................................................................ ............................... 61
E.3. Statewide Empirical Model ............................................................................... ............................... 62
E.4. Cascadia Probability Model ........................................... ............................... ............ 64
.......................
F. Results of Probability Calculations .......................................................................... ............................... 65
F.1. Probability of What? ......................................................................................... ............................... 65
F.2. Regional Probabilities ....................................................................................... ............................... 66
F.3. Probabilities for Faults ...................................................................................... ............................... 71
F.4. Probability Sensitivity Analysis ......................................... ............................... ........................ 80
G. Discussion ............................................................................................................... ............................... 84
G.1. Model Limitations and Opportunities for Future Improvements ..................... ............................... 84
G.2. Accomplishments and Key Differences From Previous Studies ...................... ............................... 87
Acknowledgments........................................................................................................ ............................... 89
References.................................................................................................................... ............................... 90
Listof Acronyms ......................................................................................................... ............................... 96
V
UCERF 2 Report
List of Appendices
A. California Fault Parameters for the National Seismic Hazard Maps and Working Group on California
Earthquake Probabilities 2007, by C. J. Wills, R. J. Weldon H,, and W. A. Bryant
B. Recurrence Interval and Event Age Data for Type A Faults, by T. E. Dawson, R. J. Weldon H,, and G.
P. Biasi
C. Monte Carlo Method for Determining Earthquake Recurrence Parameters from Short Paleoseismic
Catalogs: Example Calculations for California, by T. Parsons
D. Magnitude -Area Relationships, by R.S. Stein
E. Overview of the Southern San Andreas Fault Model, by R J. Weldon H,, G. P. Biasi, C. J. Wills, and
T.E. Dawson
F. Summary of Geologic Data and Developments of A Priori Rupture Models for the Elsinore, San
Jacinto, and Garlock Faults, by T. E. Dawson, T. K Rockwell, R J. Weldon A and C. J. Wills
G. Development of Final A -Fault Rupture Models for WGCEP/NSHMP Earthquake Rate Model 2.3, by
E. H. Field R J. Weldon H,, Y. Gupta, T. Parsons, W. J. Wills, T. E. Dawson, R. S. Stein, and M. D.
Petersen
H. WGCEP Historical California Earthquake Catalog, by K R Felker and T. Cao
I. Calculating California Seismicity Rates, by K R. Felker
J. Spatial Seismicity Rates and Maximum Magnitudes for Background, by M. D. Petersen, C. S
Mueller, A. D. Frankel, and Y. Zeng
K. A- Priori Rupture Models for Northern California Type -A Faults, by C. J. Wills, R. J. Weldon H,, and
E. H. Field 0
L. Cascadia Subduction Zone, by A. D. Frankel and M.D. Petersen
M. Empirical Estimation of Regional Time Variation in Seismicity, by K R. Felker
N. Conditional, Time - Dependent Probabilities for Segmented Type -A Faults in the WGCEP UCERF 2,
by E. H. Field and Y. Gupta
O. Paleoseismic Investigations of the Walnut Site on the San Jacinto Fault, by T. E. Fumal and K J.
Kendrick
P. Compilation of Surface Creep on California Faults and Comparison of WGCEP 2007 Deformation
Model to Pacific -North America Plate Motion, by B. A. Wisely, D. A. Schmidt, and R. J. Weldon H
vi
UCERF 2 Report
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List of Supplementary Materials
Supplementary
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Sheet 2:
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Sheet 9:
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Excel Spreadsheet
Rupture Magnitudes & Rates
Total 30 -year Rupture Probabilities
Total 5 -year Rupture Probabilities
1vr2:6.7 30 -year Rupture Probabilities
Segment Rates & Mean Recurrence Intervals
Total 30 -year Segment Probabilities
Total 5 -year Segment Probabilities
XV 6.7 30 -year Segment Probabilities
1VT2!6.7 Probabilities in WGCEP (2003: Box
Total 30 -year Probabilities on Faults
M?
[7
UCERF 2 Report
Executive Summary 11
The Uniform California Earthquake Rupture Forecast, Version 2
(UCERF 2)
2007 Working Group on California Earthquake Probabilities (WGCEP) and the
USGS National Seismic Hazard Mapping Program (NSHMP)
Executive Summary
California's 35 million people live among
some of the most active earthquake faults in the
United States. Public safety demands credible
assessments of the earthquake hazard to maintain
appropriate building codes for safe construction
and earthquake insurance for loss protection.
Seismic hazard analysis begins with an earthquake
rupture forecast —a model of probabilities that
earthquakes of specified magnitudes, locations,
and faulting types will occur during a specified
time interval. This report describes a new
earthquake rupture forecast for California
developed by the 2007 Working Group on
California Earthquake Probabilities (WGCEP
2007).
2007 Working Group on California
Earthquake Probabilities
WGCEP 2007 was organized in September,
2005, by the U. S. Geological Survey (USGS), the
California Geological Survey (CGS), and the
Southern California Earthquake Center (SCEC). It
was charged with two tasks: (1) collaborate with
the National Seismic Hazard Mapping Program
(NSHMP) in producing a revised, time -
independent forecast for California as input to the
2007 revisions of the national seismic hazard
maps, 'and (2) create a uniform, statewide, time -
dependent model that among other purposes,
Colo.uld be used by the California Earthquake
Authority (CEA) in setting earthquake insurance
rates.
The national seismic hazard maps utilize a
time- independent forecast in which the probability
of each earthquake rupture is completely
independent of the timing of all others. Time -
dependent models are based on the concept of
stress renewal: the probability of a fault rupture
drops immediately after a large earthquake
releases tectonic stress on the fault and rises again
as the stress is regenerated by continuous tectonic
loading. However, observations in California and
elsewhere show that the earthquake cycle
associated with this elastic rebound theory can be
highly irregular, owing, for example, to stress
interactions among neighboring faults. We do not
understand these interactions well enough to
model them explicitly; therefore, variations in the
earthquake cycle must be calibrated empirically
using historical observations of seismicity and
geologic data on the dazes and sizes of prehistoric
earthquakes (paleoseismology).
Time - dependent earthquake rupture forecasts,
in which the probabilities of future events are
conditioned on the dates of previous earthquakes,
have been the focus of five previous Working
Groups on California Earthquake Probabilities
(WGCEP 1988, 1990, 1995 & 2003). Each of
2 1 Executive Summary
these working groups has expanded on its
predecessors, improving the data and forecasting
methodology, and each has drawn on input from
broad cross- sections of the earth science
community. Building on this experience, we
calculate time- dependent probabilities of large
earthquakes on major faults (generally those with
the highest rates of slip) where the requisite
information is available: the expected mean
frequency of earthquakes and the elapsed time
since the last earthquake. Where such information
is lacking, we use time- independent probabilities,
which require only an estimate of earthquake
frequency.
The WGCEP 2007 study differs from previous
WGCEP efforts by:
• reporting earthquake probability for the
entire state of California instead of
subregions;
• using uniform methodology across all
regions;
• using the same earthquake rate model as
the 2007 National Seismic Hazard Map
Program;
• compiling and using updated, uniform,
and publicly accessible statewide data;
• developing new methods to make
models more rigorously adherent to
observational data, particularly fault slip
rates (moment balanced);
• making analysis tools and data available
through a readily accessible web -based
interface.
In general, we have adopted the results from
previous working groups where justified and have
updated the model only when compelled to by new
information or understanding, or by necessity to
conform. the analysis to a uniform statewide
approach and with the NSHMP assessment.
UCERF 2 Report
Review and Consensus - Building
Processes
All UCERF 2 model elements and WGCEP
2007 documents were reviewed by an internal
Scientific Review Panel (SRP) comprising experts
who were not WGCEP 2007 members. The SRP
reported to the Management Oversight Committee
(MOC), which coordinated the review and
oversaw consensus - building processes. External
oversight and review was provided by the National
Earthquake Prediction Evaluation Council
( NEPEC) and the California Earthquake
Prediction Evaluation Council ( CEPEC), as well
as CEA's Multidisciplinary Research Team.
CEPEC and NEPEC tracked model development
throughout the WGCEP 2007 process and
reviewed the final report
Advice and comment from the scientific and
engineering communities was sought regularly
through open meetings and workshops during the
several phases of UCERF development.
Participants included experts from academia,
Private and corporate providers of hazard
assessments, Colo.nsulting companies, and
government agencies. WGCEP progress was
reported at major scientific gatherings such as
annual meetings of the American Geophysical
Union, the Seismological Society of America, and
the Southern California Earthquake Center.
Model Framework
We have built on previous WGCEP and
NSHMP efforts to quantify regional earthquake
probabilities in California, using the best available
science to develop a new framework for a Uniform
California Earthquake Rupture Forecast ( UCERF).
The UCERF framework comprises a sequence of
four model types: a fault model that gives the
physical geometry of the larger, known faults; a
deformation model that gives slip rates and
•
C:
UCERF 2 Report
aseismicity factors to each fault section; an
earthquake rate model that gives the long -term
rate of all earthquakes of magnitude five or greater
(M 2: 5) throughout the region; and a probability
model that gives a probability of occurrence for
each earthquake during a specified (future) time
interval. This report presents the latest versions of
each of these models, including the statewide
time- independent earthquake rate model
incorporated into the 2007 revisions to the national
seismic hazard map (ERM 2.3) and the time -
dependent earthquake probability model derived
from ERM 2.3 ( UCERF 2). The results are
intended for use in forecasting the intensity of
ground shaking throughout California.
The model incorporates both aleatory
uncertainties (arising from natural variability) and
epistemic uncertainties (resulting from lack of
knowledge). The latter were included by
constructing a logic tree with branches
representing viable alternative hypotheses. We
restricted our consideration to data and methods
that have been published, or accepted for
publication, in peer - reviewed scientific journals or
as U.S. Geological Survey Open File Reports. If
relevant published models differed significantly,
we applied logic -tree weighting to represent the
alternatives. Generally, two alternatives were
given equal weight in the absence of any clear
evidence to favor one over the other. When there
was evidence to favor a given branch, the
assignment of relative weights was made though a
consensus - building process, which we describe for
each case.
Earthquake Rate Model
The WGCEP 2007 earthquake rate model
features a new fault geometry with more accurate
values of dip and seismogenic depth, and new
compilations of fault slip rates and paleoseismic
events. The final version, ERM 2.3, includes two
Executive Summary 13
alternative fault models for southern California
thrust -fault geometry and three alternatives
representing the uncertain slip distribution
between the southern San Andreas and San Jacinto
faults. A significant logic-tree branching involves
the choice of the magnitude -area relationship,
which is used to translate from fault slip rates to
earthquake rates; the global database of rupture
areas and magnitude determinations has
significant spread, leaving room for alternative
interpretations.
Another important model branching
incorporates alterative representations of the
earthquake rates on major faults. We compiled an
a priori earthquake rate model derived by a
community consensus of paleoseismic and other
geologic . observations. We also _calculated a
moment - balanced version of the model, which
modifies the earthquake rate to match the observed
Iong -term slip -rate data; the resulting rates were
constrained to fall within the ranges derived from
paleoseismic observations. These two models
balance a consensus of geologic and seismologic
expert opinion with strict adherence to specific
observational data.
We tested ERM 2.3 in three different ways: by
comparing the predicted magnitude- frequency
distributions of earthquakes with a unified historic
and instrumental earthquake catalog for California
and surrounding regions, by comparing integrating
measures of deformation across the plate -
boundary zone with the plate rate, and by
comparing the distribution of source types in the
model with historical data. A maj or issue was
overprediction of the rate of M >_ 6.5 earthquakes,
known informally as "the bulge ", a problem
common to previous WGCEP and NSHNO
studies. ERM 2.3 predicts an annual rate for
M?! 6.5 earthquakes of 0.32 events/yr, which
exceeds the historically observed rate of 0.24
eventslyr by about a third, though it lies within the
4 1 Executive Summary
95% confidence bounds on the observed rate
(0.13 -0.35 events/yr). In comparison, the NSHNT
2002 model for California exceeded the observed
rate by a factor of two.
Time - Dependent Earthquake Probability
Model
We tightly coordinated the development of the
earthquake rate models for California with
NSHU P, so that both the 2007 revisions of the
national seismic hazard maps and UCERF 2 are
based on ERM 2.3. Constructing an earthquake
rupture forecast from ERM 2.3 required a
probability model that specifies how events are
distributed in time, and here we departed from the
NSENT 2007 conventions by considering, along
with a time - independent (Poisson) forecast, time -
dependent forecasts that use stress - renewal
UCERF 2 Report
assumptions to condition the event probabilities
for the most active faults on the date of their last
major rupture.
Our choice of UCERF 2 model branches was
based on a careful review of all available
probability models. A particularly influential
branching is the "empirical" probability model,
which includes a geographically variable estimate
of California earthquake rate changes observed
during the last 150 years. We lack consensus on
the underlying physics that causes broad
earthquake rate changes, though there is much
promising research involving fault interactions.
Rather than applying complex physical models to
adjust probability, WGCEP 2007 relies on the
simpler empirically -based correction.
An important seismic hazard for California is
the Cascadia subduction zone, which extends
Participation Probabilities
0.00196 0.6196 0.196 146 1096 100%
Figure A. Participation probability maps, displaying the mean UCERF 2 probabilities that an individual
0.1° x 0.1° cell in the statewide grid will be involved in a fault rupture of any source type above the
specified magnitude threshold during the next 30 years. The magnitude thresholds shown here are M• 5.0,
6.7, ' and 7.7. Probability color scale is logarithmic; i.e. each decrement unit represents a 10 -fold decrease
in probability.
�U_
0
A
UCERF 2 Report
about 1200 km from Vancouver Island in British
Columbia to Cape Mendocino in California and is
capable of generating an earthquake of M 9 or
larger. Because this fault lies mostly outside the
state, we treated it as a special case with its own
logic tree, which included two rupture scenarios:
(1) M 8.8 -9.2 events that rupture the entire
Casca.dia subduction zone every 500 years on
average, and (2) M 8.0 -8.7 events whose ruptures
cover the entire zone over a period of about 500
years. A time- independent model was applied to
the M 8.0 -8.7 scenario, and a time- dependent
model to the M 8.8 -9.2 scenario.
In computing event probabilities, the branches
were weighted by expert opinion gathered in open
workshops. The UCERF 2 model has been
implemented in - a modular (object - oriented),
extensible framework using the OpenSHA
platform, so that experiments with alternative
branch weights can be easily investigated and
future updates can be quickly accommodated as
new data and methods emerge. The final
UCERF 2 logic tree incorporated 480 branches
that received nonzero weight, each of which
produces a separate set of probabilities for all
earthquakes in California. We take the mean and
spread of these results to represent the best
estimate of earthquake probability and its
sensitivity to parameter uncertainty.
Results of Probability Calculations
According to UCERF 2, a M >_ 6.7 earthquake
is virtually assured in California during the next 30
years (99.7% probability of occurrence). Larger
events are less likely: the mean 30 -year UCERF 2
estimate gives a 94% chance of a M > 7.0
earthquake, a 46% chance of a M > 7.5 shock, and
4.5% chance of a M >_ 8.0 event. The UCERF 2
range for these latter probabilities is 85 -99 %, 29-
65%, "and 0 -11 %, respectively. In addition, we
estimate a 10% probability of a M,2 8.0
Executive Summary 15
earthquake somewhere along the Cascadia
subduction zone (perhaps far from California) in
the next 30 years. We emphasize that the
probabilities calculated for the largest magnitude
events should be used with caution, because they
depend critically on rupture scenarios that involve
fault lengths longer than historically observed
ruptures, as well as an extrapolation of scaling
relationships, such as the magnitude -area
relationships, beyond the limits of the empirical
data.
Dividing the state into two approximately
equal areas, we find the 30 -year probability of a
large earthquake to be higher in the southern half:
a M >_ 6.7 earthquake has a 97% chance of
occurring in southern California in 30- years,
Colo.mpared to a 93% probability in northern
California, and the odds for a M >_ 7.5 event are
doubled (37% vs. 15 %). In addition to state -wide
and regional estimates, our report gives
probabilities for individual faults and fault
segments throughout the state, as well as a
geographically variable background rate.
The UCERF 2 earthquake rupture forecast can
be visualized by mapping the mean probability
that an element of area on a statewide grid will
include a fault rupture of any source type above a
specified magnitude threshold during the next 30
years. Figure A presents these "participation
probability" maps for three magnitude thresholds.
For events with M >_ 5.0, the areas where the
participation probabilities exceed 1% (yellow or
warmer in color) include over half the state,
reflecting the widespread distribution of California
seismicity, much of which is represented in the
model as "background." At M>_ 6.7, this same
probability level is confined to the major faults,
and at M >_ 7.7, it is generally restricted to the
longer strike -slip strands of the San Andreas fault
system.
6 1 Executive Summary
UCERF Z Report
Table A. 30 -year probability of M - 6.7 events on the Type-A faults, rounded to the nearest percent.
Table A summarizes the mean probabilities
for M >_ 6.7 events on the principal strike -slip
faults of California, which accommodate most of
the motion between the North America and Pacific
plates, and it compares our results with those of
WGCEP 1995 - -for - southern --California -and
WGCEP 2003 for the Bay Area.
The most dangerous fault is the southern part
of the San Andreas, which has a 59% probability
of generating a M >_ 6.7 earthquake in the next 30
years. This compares with 21% for the northern
San Andreas fault.
We have enough data to calculate time -
dependent earthquake probability on the principal
strike -slip faults in Table A. These faults exist
within a web of faults with lower slip rates that we
know less about, which are consequently treated as
time- independent sources. In southern California,
the contribution to overall regional probability
from these lower slip -rate faults, which include the
reverse faults of the Transverse Ranges, exceeds
that of the principal strike -slip faults.
Reliability of Results
The larger the area considered and the longer
the time considered generally makes a probability
calculation more reliable. Thus the statewide 30-
year probability values are more reliable estimates
than those for individual faults. However, even the
most reliable of our calculations are subject to
considerable sensitivity to parameters. For
example, across the 480 branches of the logic tree
we find a minimum 30 -year probability of 29% for
a M?: 7.5 earthquake, and a maximum of 65 %.
Calculations are quite sensitive to - parameter
choices on individual faults; while the mean
calculated probability on the southern San Andreas
fault is 59 %, we find that the value could
reasonably be anywhere between 22% and 94%
(see Table A).
There are known limitations with the WGCEP
2007 model, which are discussed in detail in the
main report. More research time will bring
improvements in key topical are For example,
new earthquake faults will continue to be
discovered. Improvements in our methods for
determining maximum magnitudes associated with
poorly understood faults are needed. A related
major research challenge involves improving our
ability to forecast more complex earthquake
ruptures that include fault jumps, branching, and
segment - breaking ruptures.
Comparisons with Previous Studies
The 30 -year probability of a M2:6.7
earthquake striking the San Francisco Bay Area is
63% for UCERF 2, which is indistinguishable
from the 62% value reported by WGCEP 2003
(P
,•
UCERF 2 Report
(see Table A). Moreover, the extrema calculated
from all of the UCERF 2 branches [0.41 -0.84]
approximate the 95% confidence interval of
WGCEP 2003 results for the aggregate Bay Area
probabilities [0.38 - 0.85]. This agreement indicates
that we succeeded in capturing the most important
epistemic uncertainties (in part because we were
guided by the comprehensive uncertainty analysis
of the WGCEP 2003 report).
As shown in the table, there are differences
between WGCEP 2007 and WGCEP 2003
calculations for individual fault probabilities in the
Bay Area. However, none exceed the uncertainty
ranges reported by either working group. The
differences resulted primarily from inclusion of
paleoseismic observations in UCERF 2 and the
restricted inventory -of. probability models that
could be used for our statewide analysis.
The differences in the mean 30 -year
probabilities for M >_ 6.7 events between the 1995
and 2007 studies are more significant. The most
important arise from new paleoseismic data and
analysis, new geodetic data, and an earthquake
rate model that allows a greater variety of rupture
sizes on faults. One important change is to the San
Jacinto fault, where the probability has been
halved from 61%, reported by WGCEP 1995, to
31% [14 0/6-54 %] calculated by WGCEP 2007 (see
table). Similarly, Elsinore fault probability is
halved from 24% to 11% [5916-25 %] because of the
increased array of possible earthquake magnitudes
allowed in the model.
Recommendations
The comprehensive nature of the UCERF 2
analysis has identified many opportunities for
future model improvements, and we outline in the
report specific recommendations for further
research. Examples include the relaxation of fault
segmentation and the inclusion of fault -to -fault
ruptures, which may be in part responsible for the
Executive Summary 17
"bulge" problem; the inclusion of earthquake
triggering and clustering, as manifested in
aftershock sequences; and improved magnitude-
area relationships.