Seismology and Earthquake Engineering :Introduction

Engineering for Earthquakes Earthquake Seismic Waves Geologic Effects Structural Response Losses Hazard Analysis Seismologists Geotechnical Engrs Response Analysis Geotechnical Engrs Structural Engrs Loss Analysis Structural Engrs Loss Analysts

The Earth (outside)

The Earth (inside) Hot Cold

Convection

Convection

Plates 6 continental size 14 sub-continental size

Plates White: Political boundaries Yellow: Plate boundaries Red: Epicenters

Based on continental shelves Plates

Plates

Plates

Plates

Plate Boundaries Spreading Ridge Boundary

Spreading Ridge

Eastern Pacific Ridge

Spreading Ridge Thingvellir

Plates Subduction Zone

Plates Transform Boundary

Transform Boundaries Carrizo Plain Crystal Spring Reservoir

Faults Main types: Normal Faulting

Faults Main types: Reverse Faulting

Faults Main types: Strike Slip Faulting Calaveras Fault

Basic Concepts of Seismology Elastic rebound theory Plates are in continuous motion Stresses and strains build up near boundaries Strain energy stored in crust near faults, then released Aseismic movement - slow creep in ductile rock Seismic movement - rupture of brittle rock

San Francisco Portola Valley Loma Prieta Gap Parkfield San Juan Bautista Loma Prieta Basic Concepts of Seismology Seismic Gaps seismicity

San Francisco Portola Valley Loma Prieta Gap Parkfield San Juan Bautista Loma Prieta Loma Prieta earthquake and aftershocks Loma Prieta earthquake and aftershocks Basic Concepts of Seismology Seismic Gaps

Basic Concepts of Seismology Seismic Gaps

Basic Concepts of Seismology Near-field effects “Fling” Rupture moving away from observer Rupture moving away from observer Rupture moving toward observer Rupture moving toward observer

Basic Concepts of Seismology Near-field effects “Directivity” Fault parallel Fault parallel Fault normal Fault normal Fault normal accelerations exceed fault parallel accelerations Fault normal accelerations exceed fault parallel accelerations

Basic Concepts of Seismology Earthquake size Intensity - qualitative measure of observed effects Modified Mercalli Intensity (MMI) MMI IV During 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 IV During 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 Seismology Earthquake size Intensity - qualitative measure of observed effects Modified Mercalli Intensity (MMI) MMI IV During 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 IV During 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 VII Everybody 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 VII Everybody 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 Seismology Earthquake size Intensity - qualitative measure of observed effects Modified Mercalli Intensity (MMI) MMI IV During 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 IV During 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 VII Everybody 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 VII Everybody 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 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 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

Basic Concepts of Seismology Seismic waves p-waves s-waves Love waves Rayleigh waves Body waves Body waves Surface waves Surface waves

Basic Concepts of Seismology Earthquake size Magnitude - quantitative measure of size of event Several types Local magnitude Body wave magnitude Surface wave magnitude All based on instrumental measurements All based on instrumental measurements

Basic Concepts of Seismology Earthquake size Seismic moment - measure of work done by eq. M o =  A D where  = shear modulus of rock A = rupture area D = average displacement over rupture area Units = F/L 2 x L 2 x L = F x L Work Energy

Basic Concepts of Seismology Earthquake size Moment magnitude M w = log M o 1.5 Moment magnitude Magnitude mbmb MLML MsMs M = M w Magnitude saturation Magnitude saturation

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 Waves

Strong motion seismograph Alcott Elementary, Redmond November 15, 11:10 am

Seismic Waves Triaxial accelerometers 3 components 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)