Seismically Induced Seismically Induced Ground FailureGround Failure

byby

William A. BryantWilliam A. BryantSeismic Hazards ZoningSeismic Hazards Zoning

California Geological SurveyCalifornia Geological Survey

100100thth Anniversary Earthquake Conference Anniversary Earthquake Conference Commemorating the 1906 San Francisco Commemorating the 1906 San Francisco

EarthquakeEarthquake

April 18 April 18 –– 22, 200622, 2006

Seismic Hazards Seismic Hazards Mapping Act of 1990Mapping Act of 1990

AlquistAlquist--Priolo Earthquake Priolo Earthquake Fault Zoning Act of 1972Fault Zoning Act of 1972

CGS Seismic Ground FailureCGS Seismic Ground FailureZonation ProgramsZonation Programs

This Act resulted from theThis Act resulted from theMw 6.6 1971 San Fernando earthquake.Mw 6.6 1971 San Fernando earthquake.

The AP Act originally was referred to as the The AP Act originally was referred to as the

AlquistAlquist--Priolo Geologic Hazards ActPriolo Geologic Hazards Actand was intended to address a broader scope of ground and was intended to address a broader scope of ground

deformation hazards.deformation hazards.

Immediately following the 1989 Mw 6.9 Loma Immediately following the 1989 Mw 6.9 Loma Prieta Earthquake, legislation was introduced Prieta Earthquake, legislation was introduced

and the following year enactment of the and the following year enactment of the

Seismic Hazards Mapping Act of 1990Seismic Hazards Mapping Act of 1990

AlquistAlquist--PrioloPrioloEarthquake Fault Zoning Act of 1972Earthquake Fault Zoning Act of 1972

Seismic Hazards MappingSeismic Hazards MappingAct of 1990Act of 1990

LiquefactionLiquefaction

Seismically InducedSeismically InducedLandslidesLandslides

1989 Mw 6.9 Loma Prieta Earthquake1989 Mw 6.9 Loma Prieta Earthquake

CGS Seismic Ground Failure CGS Seismic Ground Failure Zonation ProgramsZonation Programs

•• IdentifyIdentify where ground failure hazards are more likely where ground failure hazards are more likely to occurto occur

•• DelineateDelineate “zones of required investigation”“zones of required investigation”

•• TriggerTrigger “geologic or geotechnical hazards reports” “geologic or geotechnical hazards reports” that that lead to earthquake resilient construction in lead to earthquake resilient construction in hazardous hazardous areasareas

The Seismic Hazards Mapping Act (SHMA) is The Seismic Hazards Mapping Act (SHMA) is modeled after the Alquistmodeled after the Alquist--Priolo (AP) Act. Implementation Priolo (AP) Act. Implementation of the SHMA generally is the same as for the AP Act. of the SHMA generally is the same as for the AP Act.

An important distinction is that where the AP Act An important distinction is that where the AP Act mitigates surface fault rupture hazard by mitigates surface fault rupture hazard by avoidanceavoidance, the , the SHMA allows mitigation by SHMA allows mitigation by engineering designengineering design..

Comparison ofComparison ofSeismic Hazards Mapping ActSeismic Hazards Mapping Act

andandAlquistAlquist--Priolo ActPriolo Act

AdvisoryCommittee

Seismic Hazards ZoningSeismic Hazards Zoning

State Geologist

Property Owners Developers

Adopts Mandated PoliciesAdopts Mandated PoliciesReceives Review CommentsReceives Review CommentsProvides Technical AdviceProvides Technical Advice

Evaluates Regional Seismic HazardEvaluates Regional Seismic HazardDesignates Seismic Hazard ZonesDesignates Seismic Hazard ZonesProvides Advisory ServicesProvides Advisory Services

Requires Site InvestigationsRequires Site InvestigationsUpdates General PlansUpdates General PlansReviews and Approves ProjectsReviews and Approves ProjectsApplies For WaiversApplies For Waivers

Determines Hazard at SiteDetermines Hazard at SiteMitigates HazardMitigates HazardDisclosesDiscloses

State Mining & Geology Board

Cities & Counties

ALQUISTALQUIST--PRIOLOPRIOLOEARTHQUAKE FAULT ZONINGEARTHQUAKE FAULT ZONING

ACT OF 1972ACT OF 1972

1971 San Fernando Earthquake1971 San Fernando Earthquake

Intent of Act is to AvoidIntent of Act is to AvoidSurface Fault Rupture HazardSurface Fault Rupture Hazard

The AP Act addresses the seismic hazard of surface fault ruptureThe AP Act addresses the seismic hazard of surface fault ruptureby prohibiting placing most structures for human occupancy by prohibiting placing most structures for human occupancy across the traces of active faults. across the traces of active faults.

The Act also requires sellers and real estate agents to inform The Act also requires sellers and real estate agents to inform buyers whether real property being sold is within a statebuyers whether real property being sold is within a state--designated Earthquake Fault Zone. designated Earthquake Fault Zone.

Earthquake Fault Zone (EFZ) maps are issued in order to assist Earthquake Fault Zone (EFZ) maps are issued in order to assist cities and counties in avoiding the hazard of surface fault ruptcities and counties in avoiding the hazard of surface fault ruptureure

AlquistAlquist--Priolo Earthquake Fault Zoning ActPriolo Earthquake Fault Zoning Act

Damage to Residential StructureDamage to Residential Structure1992 Mw 7.3 Landers Earthquake 1992 Mw 7.3 Landers Earthquake

Foundation Damage Landers EarthquakeFoundation Damage Landers Earthquake

Photo by E. Hart

Photo by E. Hart Photo by D. Murbach

“...if development along the Chelungpu fault had occurred under AP regulations, the loss of life and property would have been greatly reduced.”

from Rubin and others, 2001, EOS, v. 82, #47

1999 Chi Chi (Taiwan) Earthquake1999 Chi Chi (Taiwan) Earthquakeandand

AlquistAlquist--Priolo Earthquake Fault Zoning ActPriolo Earthquake Fault Zoning Act

Faults in CaliforniaFaults in California

QuaternaryQuaternaryandand

Younger FaultsYounger Faults

1992 M 7.3 Landers Earthquake1992 M 7.3 Landers Earthquake

STRIKESTRIKE--SLIP FAULTSLIP FAULT

1999 M 7.5 1999 M 7.5 Chi Chi (Taiwan)Chi Chi (Taiwan)

EarthquakeEarthquake

REVERSE FAULTREVERSE FAULT

Photo by K. Kelson

NORMAL FAULTNORMAL FAULT

1954 M 7.0 Fairview Peak Earthquake1954 M 7.0 Fairview Peak EarthquakePhoto by K. Steinbrugge

AlquistAlquist--PrioloPrioloEarthquake Fault Zoning Act of 1972Earthquake Fault Zoning Act of 1972

Surface fault rupture hazard is mitigated by avoiding Surface fault rupture hazard is mitigated by avoiding placing structures across traces of hazardous faults.placing structures across traces of hazardous faults.

Earthquake Fault Zones encompass hazardous faults, Earthquake Fault Zones encompass hazardous faults, which are defined as those faults that are which are defined as those faults that are sufficiently sufficiently activeactive and and wellwell--defineddefined..

Sufficiently activeSufficiently active faults exhibit evidence of faults exhibit evidence of Holocene displacement (approx. last 11,000 years).Holocene displacement (approx. last 11,000 years).

WellWell--defineddefined -- trace detectable by trained geologist.trace detectable by trained geologist.

19401940 19791979

Surface Fault RuptureSurface Fault RuptureUsually Occurs Along PreUsually Occurs Along Pre--Existing FaultsExisting Faults

Imperial Fault Imperial Fault -- 1940 and 1979 Earthquakes1940 and 1979 Earthquakes

Evidence of Multiple EarthquakesEvidence of Multiple EarthquakesSAN ANDREAS FAULT SAN ANDREAS FAULT -- WALLACE CREEKWALLACE CREEK

Photo by R. Wallace

14 events14 events3.7 ka3.7 ka

42 events42 events

10.5 ka10.5 ka9 m9 m18571857

53 events53 events

13.3 ka13.3 ka

STATE GEOLOGISTSTATE GEOLOGIST

•• Delineates Earthquake Fault ZonesDelineates Earthquake Fault Zones

•• 1010--Region ProjectRegion Project

•• Reviews New Data for New andReviews New Data for New andRevised Earthquake Fault ZonesRevised Earthquake Fault Zones

•• Grants Waiver RequestsGrants Waiver Requests

•• Continuing ProgramContinuing Program

How the Maps are MadeHow the Maps are Made

1988-891988-891988-891988-891988-891988-891988-891988-891988-89

197719771977197719771977197719771977

1986-871986-871986-871986-871986-871986-871986-871986-871986-87

197819781978197819781978197819781978

198519851985198519851985198519851985

197619761976197619761976197619761976

200 kilometers

1981-821981-821981-821981-821981-821981-821981-821981-821981-82

1979-801979-801979-801979-801979-801979-801979-801979-801979-80

1990-911990-911990-911990-911990-911990-911990-911990-911990-91

1983-841983-841983-841983-841983-841983-841983-841983-841983-84

50 100 miles0

0 100

SANTABARBARA

KERN

TULARE

FRESNO

MADERA

SANLUIS OBISPO

KINGS

LOSANGELES

ORANGE

SANTA CLARA

SANTA CRUZ SAN BENITO

MONTEREY

INYO

MARIPOSA

SAN DIEGO

SAN FRANCISCO

CONTRA COSTA

ALAMEDA

SAN MATEO

SANJOAQUIN

STANISLAUSMONO

SAN BERNARDINO

COLUSA

TEHAMA

PLUMAS

BUTTE

NEVADA

ALPINE

CALAVERASAMADOR

SACRAMENTONAPA

SUTTER

YOLO

PLACER

LASSEN

LAKE

SONOMA

HUMBOLDT

TRINITY

MENDOCINO

SHASTA

SISKIYOU

DELNORTE

RIVERSIDE

EL DORADO

GLENN

IMPERIAL

MARIN

MERCED

MODOC

SIERRA

SOLANO

TUOLUMNE

VENTURA

California Geological SurveyCalifornia Geological Survey10 Region Fault Evaluation and Zoning Program10 Region Fault Evaluation and Zoning Program

AlquistAlquist--PrioloPrioloFault Evaluation and Zoning ProgramFault Evaluation and Zoning Program

1976 1976 -- 20012001

Faults with evidence of late Quaternary displacement were Faults with evidence of late Quaternary displacement were evaluated for possible zoning. evaluated for possible zoning.

Evaluations consisted of:Evaluations consisted of:•• Literature ReviewLiterature Review•• Air Photo InterpretationAir Photo Interpretation•• Field mappingField mapping

Results are summarized in 248 Fault Evaluation Reports.Results are summarized in 248 Fault Evaluation Reports.

Fault Evaluation ReportFault Evaluation ReportLiterature ReviewLiterature Review

Critical evaluation of available literature, both published Critical evaluation of available literature, both published and unpublished, including existing siteand unpublished, including existing site--specific specific investigations.investigations.

Age of geologic units: note youngest unit offset and oldest Age of geologic units: note youngest unit offset and oldest unit not offset.unit not offset.

Evaluate accuracy of fault locations mapped by others.Evaluate accuracy of fault locations mapped by others.

Summary of Previous MappingSummary of Previous Mapping

Fault Evaluation ReportFault Evaluation ReportAir Photo InterpretationAir Photo Interpretation

Evaluate the geomorphic expression of fault, looking for Evaluate the geomorphic expression of fault, looking for young faultyoung fault--produced landforms.produced landforms.

Identify youthful geomorphic surfaces and deposits that Identify youthful geomorphic surfaces and deposits that are offset and not offset.are offset and not offset.

Accurately plot surface traces on appropriate base maps, Accurately plot surface traces on appropriate base maps, generally at a scale of 1:24,000.generally at a scale of 1:24,000.

1978

Air Photo InterpretationAir Photo Interpretation

Use ofUse ofPrePre--development Photosdevelopment Photos

is Essentialis Essential

1924

Geomorphic ExpressionGeomorphic ExpressionRecently Active FaultsRecently Active Faults

From Wallace, 1990

Geomorphic ExpressionGeomorphic ExpressionActive Strike Slip FaultsActive Strike Slip Faults

rightright--laterally offset drainageslaterally offset drainages

linear sidehill bencheslinear sidehill benches

Photo by E. Hart

Geomorphic ExpressionGeomorphic ExpressionActive Strike Slip FaultsActive Strike Slip Faults

beheaded drainagesbeheaded drainages

linear westlinear west--facing scarp on alluvial fansfacing scarp on alluvial fans

linear drainagelinear drainage

rightright--laterally offset drainageslaterally offset drainages

Photo by R. Wallace

Geomorphic ExpressionGeomorphic ExpressionActive Reverse and Thrust FaultsActive Reverse and Thrust Faults

Photo by D. Morton

Fault Evaluation ReportFault Evaluation ReportField ReconnaissanceField Reconnaissance

Field ReconnaissanceField Reconnaissance

Verify Features Interpreted From Air PhotosVerify Features Interpreted From Air Photos

Observe and Map Small Scale Features Not Observe and Map Small Scale Features Not Visible on Air PhotosVisible on Air Photos

Estimate Ages of Surfaces Offset and Not OffsetEstimate Ages of Surfaces Offset and Not Offset

Fault Evaluation ReportFault Evaluation ReportAnnotated Fault MapAnnotated Fault Map

Fault Evaluation ReportFault Evaluation ReportGreen Valley FaultGreen Valley Fault

Fault Evaluation Report (FER) summarizes evidence Fault Evaluation Report (FER) summarizes evidence for or against fault recency.for or against fault recency.

FER provides recommendations for or against FER provides recommendations for or against encompassing faults in an Earthquake Fault Zone.encompassing faults in an Earthquake Fault Zone.

OfficialOfficialEarthquake Fault Zone Map Earthquake Fault Zone Map

Released After 6 Month Released After 6 Month Review PeriodReview Period

Index toIndex toAlquistAlquist--Priolo Earthquake Fault Zone MapsPriolo Earthquake Fault Zone Maps

(1974 (1974 –– 2005)2005)

547 Earthquake Fault Zone 547 Earthquake Fault Zone Maps issued as of 1/1/2006Maps issued as of 1/1/2006

36 Counties and 104 Cities 36 Counties and 104 Cities affectedaffected

SacramentoSacramento

LosLosAngelesAngeles

SanSanFranciscoFrancisco

SiteSite--Specific InvestigationsSpecific Investigations

Objective is to accurately locate active faults Objective is to accurately locate active faults in order to avoid placing most structures for in order to avoid placing most structures for human occupancy over potentially hazardous human occupancy over potentially hazardous faults.faults.

Fault Investigation Methods Include:Fault Investigation Methods Include:Literature ReviewLiterature Review

Aerial Photographic InterpretationAerial Photographic Interpretation

Site Observations/Geologic MappingSite Observations/Geologic Mapping

Subsurface InvestigationSubsurface InvestigationTrenchingTrenchingBorings and Test PitsBorings and Test PitsCone Penetrometer Testing (CPT)Cone Penetrometer Testing (CPT)

Geophysical InvestigationsGeophysical InvestigationsHigh Resolution Seismic ReflectionHigh Resolution Seismic ReflectionGround Penetrating RadarGround Penetrating RadarOther (Seismic Refraction, Magnetic, Other (Seismic Refraction, Magnetic,

Electrical, Resistivity, GravityElectrical, Resistivity, Gravity

Project Site Within Hayward Fault ZoneProject Site Within Hayward Fault ZoneNiles QuadrangleNiles Quadrangle

Trench ExcavationTrench ExcavationSiteSite--Specific FaultSpecific Fault--Rupture Hazard InvestigationRupture Hazard Investigation

Trench Locations forTrench Locations forSpecific Structure FootprintSpecific Structure Footprint

From UGS, Misc. Pub. 03-6

Trench Locations for Project SiteTrench Locations for Project Site

From UGS, Misc. Pub. 03-6

Hayward Fault Zone Hayward Fault Zone Site Investigation for Site Investigation for

CondominiumCondominium ComplexComplex

Logs for TrenchesLogs for TrenchesTTTT--C and TTC and TT--CC

Bonilla and Lienkaemper (1991) concluded that 45% of faults die Bonilla and Lienkaemper (1991) concluded that 45% of faults die out upward, even though rupture continued to the ground surface.out upward, even though rupture continued to the ground surface.StrikeStrike--slip and reverse faults comprise greater than 70% of this slip and reverse faults comprise greater than 70% of this fraction. Therefore, a fault strand overlain by an apparently fraction. Therefore, a fault strand overlain by an apparently undisturbed deposit is not necessarily older than the deposit.undisturbed deposit is not necessarily older than the deposit.

Faults in unconsolidated deposits:Faults in unconsolidated deposits:Gouge reported in only 15% of exposuresGouge reported in only 15% of exposuresSlickensides noted in only about 10% of exposuresSlickensides noted in only about 10% of exposures

Trench ConsiderationsTrench ConsiderationsBonilla and Lienkaemper, 1991, Bonilla and Lienkaemper, 1991, Factors affecting the recognition of Factors affecting the recognition of

faults exposed in exploratory trenchesfaults exposed in exploratory trenches: USGS Bulletin 1947.: USGS Bulletin 1947.

Required reading for geologists who write or reviewRequired reading for geologists who write or reviewreports evaluating fault activityreports evaluating fault activity

AgeAge--Dating TechniquesDating Techniques

Relative Dating Methods:Relative Dating Methods:Soil Profile DevelopmentSoil Profile DevelopmentDegree of Land Surface PreservationDegree of Land Surface Preservation

Isotopic MethodsIsotopic Methods1414CCCosmogenic NuclideCosmogenic Nuclide

Radiogenic MethodsRadiogenic Methods

Thermoluminescence (TL)Thermoluminescence (TL)

Optically Stimulated Luminescence (OSL)Optically Stimulated Luminescence (OSL)Correlation MethodsCorrelation Methods

TephrochronologyTephrochronology

Marine Terrace CorrelationMarine Terrace Correlation

Glacial Event CorrelationGlacial Event Correlation

CONDOMINIUMSCONDOMINIUMS

SET BACKSET BACK

FROM FROM

HAYWARD FAULTHAYWARD FAULT

Result of Fault InvestigationResult of Fault Investigation

Photo by C. Real

SetbacksSetbacks

Setback from active fault generally 50 feet (15 m). Language in California Code of Regulations (sec 3603) states “..as the area within 50 feet of such active faults shall be presumed to be underlain by active branches of that fault unless proven otherwise by an appropriate geologic investigation… no such structures shall be permitted in this area.”

Setback recommendations should consider the style Setback recommendations should consider the style and complexity of faulting at the site and the accuracy and complexity of faulting at the site and the accuracy of fault location. In general, the hanging wall of dipof fault location. In general, the hanging wall of dip--slip slip faults will have a greater setback width than the faults will have a greater setback width than the footwall.footwall.

Digital AP ProductsDigital AP Products

Selected ReferencesSelected References

Bonilla and Lienkaemper, 1991, Factors affecting the recognition of faults exposed in exploratory trenches: U.S. Geological Survey Bulletin 1947.

California Geological Survey, 2002, Guidelines for evaluating the hazard of surface fault rupture: California Geological Survey Note 49.

California Geological Survey, 2002, General guidelines for reviewing geologic reports: California Geological Survey Note 41.

Christenson, G.E., Batatian, L.D., and Nelson, C.V., 2003, Guidelines for evaluating surface-fault-rupture hazards in Utah: Utah Geological Survey Miscellaneous Publication 03-06.

Hart, E.W., and Bryant, W.A., 1999, Fault-rupture hazard zones in California: Division of Mines and Geology Special Publication 42.

McCalpin, J.P., (ed), 1996, Paleoseismology: Academic Press.

Noller, J.S., Sowers, J.M., and Lettis, W.R. (eds), 2000, Quaternary geochronology, methods and applications: Washington D.C., American Geophysical Union AGU Reference Shelf 4.

Internet ResourcesInternet ResourcesAlquistAlquist--Priolo ActPriolo Act

http://www.conservation.ca.gov/CGS/rghm/aphttp://www.conservation.ca.gov/CGS/rghm/ap

Special Publication 42Special Publication 42ftp://ftp.consrv.ca.gov/pub/dmg/pubs/sp/Sp42.pdf

CGS Fault Rupture Guidelines (Note 49)CGS Fault Rupture Guidelines (Note 49)http://www.consrv.ca.gov/CGS/information/publications/cgs_notes

Utah Geological Survey Fault Rupture GuidelinesUtah Geological Survey Fault Rupture Guidelineshttp://geology.utah.gov/online/mp/mp03-06.pdf

CGS Digital Fault Activity MapCGS Digital Fault Activity Maphttp://www.conservation.ca.gov/CGS/information/publications/QuaternaryFaults_ver2.htm