Earthquake Hazard Assessment Studies: temporal variability

Earthquake Hazard Assessment Studies:temporal variability

Dr. Ken HudnutDr. Ken HudnutChief, So. Calif. Earthquake Hazard Assessment ProjectChief, So. Calif. Earthquake Hazard Assessment ProjectEarthquake Hazards Team Earthquake Hazards Team U. S. Geological SurveyU. S. Geological Survey

SESAC6/11/03 Ken Hudnut

Plenty of eq.’s to study and new data

• Landers 1992 Landers 1992 (including Joshua Tree (including Joshua Tree and Big Bear)and Big Bear)

• 1994 Northridge1994 Northridge• 1999 Hector Mine1999 Hector Mine

• 250+ SCIGN stations250+ SCIGN stations• CMM3 available nowCMM3 available now• Total of over 60 Total of over 60

publications using publications using SCIGN data so farSCIGN data so far


1st Year• Combined time

series (1996-2002)

3rd Year• Real-time earth-

quake response

5th Year• Resolve rates on

primary LA basin

faults (and others)

SCIGN Data Products


1st Year• Complete and

distribute CMM3

3rd Year• Integrate InSAR

with GPS forvertical defor-mation rates

5th Year• Resolve rate dis-

crepanciesbetween geologyand geodesy

SCEC Tectonic Geodesy


Los Angeles metropolitan region

• Bawden et al., 2002 Bawden et al., 2002 NatureNature paper paper

• Seasonal variations Seasonal variations in SCIGN data in SCIGN data correlated with water correlated with water table changestable changes

• Removal of this Removal of this noise enabled a noise enabled a refined velocity map refined velocity map for the urban areafor the urban area


LA hazard - the SCEC way

• Master model Master model envisioned by Akienvisioned by Aki

• Must integrate many Must integrate many types of informationtypes of information

• Combine GPS with Combine GPS with the deep fault the deep fault geometry (from geometry (from imaging and imaging and seismicity, etc.) and seismicity, etc.) and 3D structure3D structure

• Employ novel Employ novel modeling methodsmodeling methods

D. Argus, JPL


Improving hazard assessmentImproving hazard assessment

• Temporal variations do Temporal variations do occur:occur:• Clustering (e.g., Basin & Clustering (e.g., Basin &

Range, ECSZ, Asia)Range, ECSZ, Asia)• Discrepant geological Discrepant geological

and geodetic ratesand geodetic rates• Sequences involving Sequences involving

fault interaction (e.g., fault interaction (e.g., Joshua Tree - Landers - Joshua Tree - Landers - Big Bear - Hector Mine; Big Bear - Hector Mine; Anatolian system, etc.)Anatolian system, etc.)

• Implement robust Implement robust research findings into research findings into hazard assessmenthazard assessment

Courtesy Anke Friedrich


Examples of differences in rateExamples of differences in rate Garlock faultGarlock fault

Geologic rate 7 +/- 2 mm/yrGeologic rate 7 +/- 2 mm/yr Geodetic rate 2 +/- 2 mm/yrGeodetic rate 2 +/- 2 mm/yr Geodesy Geodesy << Geology => Geology => weak lower crustweak lower crust

Eastern California Shear ZoneEastern California Shear Zone Geologic rate summed over all faults is ~6 mm/yrGeologic rate summed over all faults is ~6 mm/yr Geodetic rate across ECSZ is ~10–12 mm/yrGeodetic rate across ECSZ is ~10–12 mm/yr Geodesy Geodesy >> Geology => Geology => clustering or new higher tectonic rate?clustering or new higher tectonic rate?

Imperial ValleyImperial Valley Geologic rate of 20 mm/yrGeologic rate of 20 mm/yr Geodetic rate across valley of ~50 mm/yr => Geodetic rate across valley of ~50 mm/yr => missing a major fault?missing a major fault?

Sierra Madre – Cucamonga fault zoneSierra Madre – Cucamonga fault zone Geologic rate of 0.5 mm/yrGeologic rate of 0.5 mm/yr Geodetic rate of Geodetic rate of aa

Raymond faultRaymond fault Geologic rate of 1.5-4 mm/yr Geologic rate of 1.5-4 mm/yr Geodetic rate of Geodetic rate of bb

a + b ~ 6-8 mm/yr


Fault interaction studiesFault interaction studies

• Emerging view of Emerging view of large events as a large events as a composite of sub-composite of sub-events or asperitiesevents or asperities

• Dynamic triggeringDynamic triggering• Static triggeringStatic triggering

• Important to study Important to study analogous eventsanalogous events

• Cascading rupture - Cascading rupture - order in chaos?order in chaos? Bayarsayhan et al., 1996

Kurushin et al., 1998

1857 San Andreas

1957 Gobi-Altay


Serkan Bozkurt, Tom Fumal, & Ross Stein, USGS


NW SJF Scenario Stress Changes

Greg Anderson, USGS


SJF event with jumpingSJF event with jumping

Brad Aagaard, USGS


Preliminary conclusions of Anderson and AagaardPreliminary conclusions of Anderson and Aagaard

• InteractionsInteractions• SM/CF to SAF/SJF: difficult to triggerSM/CF to SAF/SJF: difficult to trigger

• SJF to SM/CF: possible to triggerSJF to SM/CF: possible to trigger

• SE SAF to SM/CF: possible to triggerSE SAF to SM/CF: possible to trigger

• Geometry is criticalGeometry is critical

• If latter two are correct, highly dangerousIf latter two are correct, highly dangerous• Much bigger earthquakes (composite events, like 1957 G-A)Much bigger earthquakes (composite events, like 1957 G-A)

• Rupture near Riverside, SB, Palm Springs, & LARupture near Riverside, SB, Palm Springs, & LA

• Directivity & basin reverberations can be explicitly studied for Directivity & basin reverberations can be explicitly studied for several of the most plausible scenario eventsseveral of the most plausible scenario events


Hector Mine 1999 post-seismic

• Pre-1992 Landers Pre-1992 Landers sequence data from sequence data from USGS Crustal Strain USGS Crustal Strain Project showed NE-Project showed NE-trending zone of NW-SE trending zone of NW-SE oriented extensionoriented extension

• Feeder from Gulf of Feeder from Gulf of California to ECSZCalifornia to ECSZ

• Post-1999 Hector Mine Post-1999 Hector Mine revealed 30 km inboard revealed 30 km inboard shift of right-lateral shift of right-lateral shear boundaryshear boundary


ECSZ temporalECSZ temporalvariationsvariations

• Savage et al., in prep. Savage et al., in prep. data confirm our model data confirm our model for block breakawayfor block breakaway

• Nikolaidis et al. vertical Nikolaidis et al. vertical rates from SCIGN -rates from SCIGN -suggest rate changessuggest rate changes

R. Nikolaidis, UCSD

Hudnut et al., 2002


New methods and data integration

• precise topographic mapping of surface ruptures and active fault scarps

representation of actual fault ruptures recorded and preserved in unprecedented detail

Airborne platform navigationmust be highly precise andrequires high-rate GPS data


Earthquake Hazard Assessment Studies:temporal variability

Temporal variations do occur:Temporal variations do occur: ClusteringClustering Discrepant geological and geodetic ratesDiscrepant geological and geodetic rates Sequences involving fault interactionSequences involving fault interaction

Implement robust research findings into Implement robust research findings into hazard assessmenthazard assessment

We can achieve the ‘physical master model’We can achieve the ‘physical master model’• Detailed fault interaction simulations and scenario Detailed fault interaction simulations and scenario

earthquakes within a realistic representation of the earthquakes within a realistic representation of the physical system, and governed by realistic physicsphysical system, and governed by realistic physics

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Earthquake Hazard Assessment Studies: temporal variability