seismology and earthquake engineering :introduction
TRANSCRIPT
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)