ShakeOut Earthquake ScenarioGround Motions

Kenneth W. HudnutU. S. Geological Survey

Earthquake Research Affiliates Pasadena, California

9 May 2008

ShakeOut Earthquake ScenarioGround Motions

Kenneth W. HudnutU. S. Geological Survey

Earthquake Research Affiliates Pasadena, California

9 May 2008

U.S. Department of the InteriorU.S. Geological Survey

USGS Multi-Hazards Demonstration Project• Lucy Jones, Chief Scientist• Dale Cox, Project Manager• Suzanne Perry, Staff Scientist

• Earthquake Scenario Coordinators: – Dan Ponti, Anne Wein, Rich Bernknopf, and Ken Hudnut (all at USGS), Mike

Reichle and Jerry Treiman (CGS), Keith Porter and Dennis Mileti (Univ. of Colorado), Jim Goltz (OES), Hope Seligson (MMI Eng.), and Kim Shoaf (UCLA)

• ShakeOut Earthquake Contributors - Source Description, Surface Faulting and Ground Motions:

– Brad Aagaard and Ned Field (USGS), Rob Graves* (URS), Lisa Star and Jonathan Stewart (UCLA), Thomas Jordan,* Gideon Juve,* Philip Maechling,* David Okaya,* Scott Callaghan* (USC), Jacobo Bielak,* Ricardo Taborda,* Leonardo Ramirez-Guzman,* Julio Lopez,* and David O'Hallaron* (CMU) and John Urbanic* (PSC), Geoff Ely* (SDSU/UCSD), Kim Olsen,* Luis Dalguer* and Steve Day* (SDSU), Yifeng Cui,* Jing Zhu,* Timothy Kaiser,* Amit Chourasia,* and Reagan Moore* (SDSC), Chen Ji (UCSB), Swami Krishnan, Matt Muto and Jeroen Tromp (Caltech)

* participant in the SCEC/CME collaboration, funded by the National Science Foundation

Economic Activity

Time

Projected activity

For one specific natural hazard event:

‘Disaster’(a few yrs.)

‘Catastrophe’(decades)

even

t

USGS/CGS/SCEC & CEA - UCERF (4/21/08)

A San Andreas “Big One” isfar bigger than Northridge 1994

What is meant by “Big One” exactly…?

- fault length is 300 km (15 x)- rupture duration is 90 sec (10 x)

- shaking duration is 180 sec (15 x)

M 7.8 “great” >> M 6.7amplitude (15 x) & energy (~30 x)

ShakeOut Scenario Earthquake • Not a prediction - a plausible event• First step: define the rupture length

1812

1857

1680

?

?

Possible early/pre-historic earthquake rupture correlations:

- Conservative correlations result in 6 events in 1200 years

- Recurrence Interval ~150 years without latest ‘open’ interval

- Currently, elapsed time of ~ 300 years appears longer than any previous recurrence interval

A call for the most reliable data: Hard data versus soft data

Examples: SoSAFE Project, B4 LiDAR project on San Andreas, multi-investigator trench studies

Courtesy of Gordon Seitz, Pat Williams, Ray Weldon & Belle Philobosian

Digging deep into the San Andreas fault,because the past may be the key to the future

ShakeOut - Static Rupture Description

thrusting& folding

18571857 18121812 16801680

20±310±316±322±628±7

Slip Rates:

SE endBombayBeach

NW endLake

Hughes

1857185716801680

18121812

20±3 10±3 16±3 22±6 28±7

WGCEP Slip Rates:

thrusting& folding

rupture propagation direction

slip

(m

eter

s)

Kinematic Rupture Model (beta v.1)

SSA 2007 presentationAagaard, Hudnut & Jones

web site w/ RefEq standard rupture model format file

Slip (meters)

SE (BB) NWCPSGP

View is from a pointto the NE and abovethe San Andreas fault

Mw7.8 ‘ShakeOut’ Scenario (GG’08 Nov. 13, 2008)

• San Andreas ‘Big One’ simulated

earthquake

• Initiation near Bombay Beach

(unilateral rupture to the NW)

• Disruption of critical lifeline

infrastructure (freeway, internet,

power and gas lines) along surface

rupture

• Strong shaking throughout the

region, including urban areas

Surface Slip and Modified Mercalli Intensities for ShakeOut scenario earthquake. Credits: Rob Graves (SCEC-CME; URS / USC) Brad Aagaard (USGS); ShakeMap Integration thanks to Vince Quitoriano (USGS), Wan Lin (USGS), Keith Porter (Univ. of Colorado) and David Wald (USGS)

Kinematic rupture models

• Kinematic Rupture Description - Aagaard, Hudnut & Jones– Two SCEC workshops; CGS/USGS/SCEC - ‘A-faults’ & SoSAFE– 1D slip distribution construction - background slip model– Mapped onto SCEC CFM and CFM-tin fault geometry– Source physics ‘first principals’ and empirical relations to construct

details of the kinematic rupture description; presented at SSA 2007– v 1.1 was superceded by v 1.2; v 1.2 included NW-to-SE and bi-

lateral

• URS/USC - v 1.1, v 1.2 (SE-NW, NW-SE, bi-lateral)• CMU/PSC - v 1.1• SDSU/SDSC - v 1.1• UCSB/Caltech - v 1.1, v 1.2 (SE-NW, NW-SE, bi-lateral)

ShakeOut v 1.1 vs. v 1.2

Surface slip - similar but‘rougher’ in v 1.2

Ground motions - similarin v 1.2 and v 1.1; comparisonsshown at sites of tall buildings

Courtesy of Rob Graves; URS, SCEC/CME

Kinematic rupture models

• Kinematic Rupture Description - Aagaard, Hudnut & Jones– Two SCEC workshops; CGS/USGS/SCEC - ‘A-faults’ & SoSAFE– 1D slip distribution construction - background slip model– Mapped onto SCEC CFM and CFM-tin fault geometry– Source physics ‘first principals’ and empirical relations to construct

details of the kinematic rupture description; presented at SSA 2007– v 1.1 was superceded by v 1.2; v 1.2 included NW-to-SE and bi-

lateral

• URS/USC - v 1.1, v 1.2 (SE-NW, NW-SE, bi-lateral)• CMU/PSC - v 1.1• SDSU/SDSC - v 1.1• UCSB/Caltech - v 1.1, v 1.2 (SE-NW, NW-SE, bi-lateral)

Kinematic rupture comparison

QuickTime™ and aH.264 decompressor

are needed to see this picture.

Rupture unzips SE to NW, taking 90 seconds;Shaking lasts >3 min.’s in LA & Ventura

Southern California Earthquake Center

QuickTime™ and aH.264 decompressor

are needed to see this picture.

• Kinematic– Forward model– A priori fault geometry

(SCEC CFM), slip and rupture process

– Ground motions computed are physics-based

– 4 groups took this approach and produced similar ground motions (URS/USC, CMU/PSC, SDSU/SDSC, UCSB/Caltech)

• Dynamic– Spontaneous rupture

modeled– A priori fault geometry

(vertical - simplified) and friction law on the fault specified

– Match surface slip of ShakeOut kinematic rupture description

– Work is ongoing by SCEC/CME group

Dynamic vs. Kinematic

Dynamic Model(Kim Olsen, Luis Dalguer, Steve Day)

Onset and Duration of Shaking

www.ShakeOut.org

Kenneth W. Hudnut, Ph.D.

Geophysicist, USGS

525 S. Wilson Ave.

Pasadena, CA 91106

hudnut@usgs.gov

(626)583-7232