Faults and Earthquakes Faults and Earthquakes

BASIC DEFINITIONSBASIC DEFINITIONS FAULTFAULT: A surface or narrow zone : A surface or narrow zone

along which one side has moved along which one side has moved relative to the other. relative to the other.

Faults are classified based upon Faults are classified based upon their direction of movement. their direction of movement.

HANGING WALL vs FOOTWALLHANGING WALL vs FOOTWALL A fault divides rock into two A fault divides rock into two fault blocksfault blocks For any inclined fault, the block above the fault is For any inclined fault, the block above the fault is

the the hanging wall blockhanging wall block, and the block below the , and the block below the fault is the fault is the footwall blockfootwall block

www.data.scec.org/Module/footnt02.html

CLASSIFICATION of DIP-SLIP CLASSIFICATION of DIP-SLIP FAULTSFAULTS

NORMAL FAULTSNORMAL FAULTS: Dip-slip faults on which the : Dip-slip faults on which the hanging wall moves down relative to the footwallhanging wall moves down relative to the footwall• Place younger rocks on older rocksPlace younger rocks on older rocks• Form in regions of lateral extensionForm in regions of lateral extension

www.data.scec.org/Module/footnt02.html

EXAMPLES OFEXAMPLES OFNORMAL FAULTSNORMAL FAULTS

Conjugate Normal Faults,Canyonlands National Parkdarkwing.uoregon.edu/~millerm/conjN1.html

Normal Fault Scarps, Turkeywww.msnucleus.org/.../pt/hazards/4/pth4_1a.html

Outcrop scale normal faults

CLASSIFICATION of DIP-SLIP CLASSIFICATION of DIP-SLIP FAULTSFAULTS

THRUST or REVERSE FAULTSTHRUST or REVERSE FAULTS: Dip-slip faults on : Dip-slip faults on which the hanging wall moves up relative to the which the hanging wall moves up relative to the footwallfootwall• Place older rocks on younger rocksPlace older rocks on younger rocks• Form in regions of lateral compressionForm in regions of lateral compression

www.data.scec.org/Module/footnt02.html

EXAMPLES OFEXAMPLES OFTHRUST FAULTSTHRUST FAULTS

Thrust Fault in Concrete from 1964 Quake,Anchorage, Alaskawww.ucmp.berkeley.edu/.../alaska/0709log.html

Thrust Fault in Sedimentswww001.upp.so-net.ne.jp/fl-fg/05-01.htm

Outcrop scale thrust faultswww.pitt.edu/.../7Structures/ReverseFaults.html

CLASSIFICATION of STRIKE-SLIP CLASSIFICATION of STRIKE-SLIP FAULTSFAULTS

RIGHT-LATERAL (DEXTRAL) FAULTSRIGHT-LATERAL (DEXTRAL) FAULTS: Strike-slip : Strike-slip faults across which the block moves to the rightfaults across which the block moves to the right

LEFT-LATERAL (SINISTRAL) FAULTSLEFT-LATERAL (SINISTRAL) FAULTS: Strike-slip : Strike-slip faults across which the block moves to the rightfaults across which the block moves to the right

EXAMPLES OFEXAMPLES OFSTRIKE-SLIP STRIKE-SLIP FAULTSFAULTS

San Andreas Fault, CAhttp://education.usgs.gov/california/pp1515/chapter2/fig2-21.jpg

Right Lateral Slip, Izmit, Turkey, 1999 Quakehttp://www.geo.uib.no/jordskjelv/

index.php?topic=earthquakes&lang=en

Right Lateral Fault in Asphaltwww.uwsp.edu/.../fault_transform_photo.html

EarthquakesEarthquakes

Epicenter and FocusEpicenter and Focus

Seismograph and Seismograph and SeismogramSeismogram

Determining Determining Earthquake Earthquake

DistanceDistance

Locating an EpicenterLocating an Epicenter

Global SeismicityGlobal Seismicity

Richter Scale…Richter Scale…A Measure of Earthquake A Measure of Earthquake

SizeSize

Convergent Plate BoundariesConvergent Plate Boundaries

SumatraSumatra

Site of M9.3 Site of M9.3 Earthquake,Earthquake,

December 26, December 26, 20042004

Convergent Plate BoundariesConvergent Plate Boundaries

ChileChile

Site of M9.5 Site of M9.5 Earthquake,Earthquake,

May 22, 1960May 22, 1960

Convergent Plate BoundariesConvergent Plate Boundaries

PakistanPakistan

Site of M5.2 Site of M5.2 Earthquake,Earthquake,

July 16,July 16,20052005

Transform Plate BoundariesTransform Plate Boundaries

San Andreas San Andreas FaultFault

Boundary Boundary Between the Between the

North North American and American and Pacific PlatesPacific Plates

San Andreas San Andreas FaultFault

San FranciscoSan FranciscoSite of M7.8 Site of M7.8 Earthquake, Earthquake,

April 18,April 18,19061906

Plate BoundariesPlate Boundaries

Seismicity of the US, 1968-2003, M>3.5

NE Seismicity1977-1999(22 Years)

Blue Circles:M≥4

Seismic Zones for Building CodesSeismic Zones for Building Codes

Liquifaction…Liquifaction…

Manhattan Site Classes,Census Track - Based

A Hard Rock 0.8

B Firm Rock 1.0

C Firm Soil 1.7

D Soil 2.4

E Soft Soil 3.5

Amplification at 1.0 Hz