seismology and earthquake engineering :introduction

Seismology and Earthquake Seismology and Earthquake Engineering :IntroductionEngineering :Introduction

Engineering for EarthquakesEngineering for Earthquakes

Earthquake

Seismic Waves

Geologic Effects

Structural Response

Losses

Hazard Analysis

SeismologistsGeotechnical Engrs

Response Analysis

Geotechnical EngrsStructural Engrs

Loss AnalysisStructural EngrsLoss Analysts

The Earth The Earth (outside)(outside)

The Earth (inside)

Hot

Cold

ConvectionConvection

ConvectionConvection

PlatesPlates

6 continental size14 sub-continental size

PlatesPlates

White: Political boundariesYellow: Plate boundariesRed: Epicenters

Based on continental shelves

PlatesPlates

PlatesPlates

PlatesPlates

PlatesPlates

Plate BoundariesPlate Boundaries Spreading Ridge Boundary

Spreading Ridge

Spreading Ridge

Eastern Pacific RidgeEastern Pacific Ridge

Spreading Ridge

ThingvellirThingvellir

PlatesPlatesSubduction Zone

Subduction ZoneSubduction Zone

PlatesPlatesTransform Boundary

Transform BoundariesTransform Boundaries

Carrizo PlainCarrizo PlainCrystal Spring Reservoir

FaultsFaults

Main types:

Normal FaultingNormal Faulting

FaultsFaults

Main types:Main types:

Reverse FaultingReverse Faulting

FaultsFaults

Main types:

Strike Slip FaultingStrike Slip Faulting

Calaveras Fault

Basic Concepts of SeismologyBasic Concepts of Seismology

Elastic rebound theory

Plates are in continuous motionStresses and strains build up near boundariesStrain energy stored in crust near faults, then released

Aseismic movement - slow creep in ductile rockSeismic movement - rupture of brittle rock

San

F

ranc

isco

Por

tola

V

alle

y

LomaPrietaGap

Par

kfie

ld

San

Jua

nB

autis

ta

Lom

a P

rieta

Basic Concepts of SeismologyBasic Concepts of Seismology

Seismic Gaps

1969-89 seismicity1969-89 seismicity

San

F

ranc

isco

Por

tola

V

alle

y

LomaPrietaGap

Par

kfie

ld

San

Jua

nB

autis

ta

Lom

a P

rieta

Loma Prieta earthquake and

aftershocks

Loma Prieta earthquake and

aftershocks

Basic Concepts of SeismologyBasic Concepts of Seismology

Seismic Gaps

Basic Concepts of SeismologyBasic Concepts of Seismology

Seismic Gaps

Basic Concepts of SeismologyBasic Concepts of Seismology

Near-field effects

“Fling”

Rupture movingaway from observer

Rupture movingaway from observer

Rupture movingtoward observer

Rupture movingtoward observer

Basic Concepts of SeismologyBasic Concepts of SeismologyBasic Concepts of SeismologyBasic Concepts of Seismology

Near-field effectsNear-field effects

“Directivity”“Directivity” Faultparallel

Faultparallel

Faultnormal

Faultnormal

Fault normalaccelerationsexceed faultparallel accelerations

Fault normalaccelerationsexceed faultparallel accelerations

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Intensity - qualitative measure of observed effectsModified Mercalli Intensity (MMI)

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Intensity - qualitative measure of observed effectsModified Mercalli Intensity (MMI)

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

MMI VIIEverybody runs outdoors; damage negligible in buildings of good design and construction, slight to moderate in well-built structures, considerable in poorly built or badly designed structures; some chimneys broken; noticed by persons driving motor cars

MMI VIIEverybody runs outdoors; damage negligible in buildings of good design and construction, slight to moderate in well-built structures, considerable in poorly built or badly designed structures; some chimneys broken; noticed by persons driving motor cars

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Intensity - qualitative measure of observed effectsModified Mercalli Intensity (MMI)

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

MMI IVDuring the day felt indoors by many, outdoors by few; at night some awakened; dishes, windows, doors disturbed; walls make cracking sound; sensation like heavy truck striking building; standing motor cars rocked noticeably

MMI VIIEverybody runs outdoors; damage negligible in buildings of good design and construction, slight to moderate in well-built structures, considerable in poorly built or badly designed structures; some chimneys broken; noticed by persons driving motor cars

MMI VIIEverybody runs outdoors; damage negligible in buildings of good design and construction, slight to moderate in well-built structures, considerable in poorly built or badly designed structures; some chimneys broken; noticed by persons driving motor carsMMI X

Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked; rails bent; landslides considerable from river banks and steep slopes; shifted sand and mud; water splashed over banks

MMI XSome well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked; rails bent; landslides considerable from river banks and steep slopes; shifted sand and mud; water splashed over banks

Basic Concepts of SeismologyBasic Concepts of Seismology

Seismic waves

p-waves

s-waves

Love waves

Rayleigh waves

Body waves

Body waves

Surface waves

Surface waves

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Magnitude - quantitative measure of size of eventSeveral types

Local magnitudeBody wave magnitudeSurface wave magnitude

All based oninstrumental

measurements

All based oninstrumental

measurements

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Seismic moment - measure of work done by eq.

Mo = A D

where = shear modulus of rockA = rupture areaD = average displacement over rupture area

Units = F/L2 x L2 x L = F x L

Work EnergyWork Energy

Basic Concepts of SeismologyBasic Concepts of Seismology

Earthquake size

Moment magnitude

Mw = ------------ - 10.7log Mo

1.5

Moment magnitude

Mag

nitu

de

mb

ML

Ms

M = M w

Magnitudesaturation

Magnitudesaturation

Earthquake Size

Shakes ground horizontally and vertically

Wave damages structures

Shakes ground horizontally and vertically

Wave damages structures

Similar to “S” wave Moves ground

horizontally

Similar to “S” wave Moves ground

horizontally

Like rolling ocean wave Shakes ground vertically

and horizontally

Like rolling ocean wave Shakes ground vertically

and horizontally

Arrives first Sometimes audible

Arrives first Sometimes audible

Seismic WavesSeismic Waves

Seismic WavesSeismic Waves

Strong motion seismograph

Alcott Elementary, Redmond

November 15, 11:10 am

Seismic WavesSeismic Waves

Triaxial accelerometers3 components

Horizontal motions are very important

Horizontal motions are very important

So What?

• Deaths and injuries

• Economic loss

Hall of Fame (famous earthquakes)

1906 San Francisco

Hall of Fame (famous earthquakes)

1964 Niigata

Hall of Fame (famous earthquakes)

1964 Alaska

Hall of Fame (famous earthquakes)

1960 Chile

Hall of Fame (famous earthquakes)

1971 San Fernando

Hall of Fame (famous earthquakes)

1985 Mexico City

Hall of Fame (famous earthquakes)

1989 Loma Prieta

Hall of Fame (famous earthquakes)

1994 Northridge

Hall of Fame (famous earthquakes)

1995 Kobe

Hall of Fame (famous earthquakes)

1999 Chi Chi (Taiwan)