earthquake hazard assessment studies: temporal variability
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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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
Serkan Bozkurt, Tom Fumal, & Ross Stein, USGS
SESAC6/11/03 Ken Hudnut
NW SJF Scenario Stress Changes
Greg Anderson, USGS
SESAC6/11/03 Ken Hudnut
SJF event with jumpingSJF event with jumping
Brad Aagaard, USGS
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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
SESAC6/11/03 Ken Hudnut
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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