Lecture 19

Earthquakes

Lecture Outline

I DefinitionsII Properties

A) Focus and EpicenterB) Seismic Waves

i. Body Wavesii. Surface Waves

C) Strengthi. Intensityii. Magnitude

III EffectsIV Plate Tectonics and Earthquakes

A) Plate Boundariesi. Divergentii. Convergentiii. Transform

B) Subduction AngleV Conclusions

Lecture 19i

Definitions

earthquake - the vibration felt when energy is released

fault - fracture or fracture zone along which there has

fault line - the intersection of a fault with the surface of the

abruptly by the sudden displacement of rock along faults within the Earth's crust

been displacement of the sides relative to oneanother

Earth, or the trace of a fault on a surface of reference

Tectonic DeformationElastic Rebound

Tectonic DeformationElastic Rebound

Properties

Focus

Epicenter

Seismic Waves

Stength

Seismic Waves

Body Waves

Surface Waves

P (primary) Waves

S (secondary) Waves

Love Waves

Rayleigh Waves

Seismic WavesBody Waves P (Primary)Waves

S (Secondary)Waves

Seismic WavesBody Waves - Refraction

Seismic WavesBody Waves - Pathways

Seismic WavesSurface Waves

Rayleigh Waves

Love Waves

Detecting Seismic Waves

Detecting Seismic Waves

Detecting Seismic Waves

Detecting Seismic Waves

Detecting Seismic WavesFinding Epicenter

Detecting Seismic Waves

Detecting Seismic WavesFirst Motion Analysis

Detecting Seismic WavesFirst Motion Analysis - Strike Slip

Faults

Seismic Strength

Mercalli Intensity Scale

Richter Scale (Magnitude)

Moment Magnitude

Seismic StrengthIntensity

Measure of severity of ground shaking

Decreases with distance from focus

Shallow focus (<30km) > deep focus (>100km)

Greater on unconsolidated sediment than on bedrock

Seismic StrengthModified Mercalli Intensity Scale

1811 New Madrid Earthquake1906 San Francisco Earthquake

Seismic StrengthRichter Magnitude Scale

Seismic StrengthRichter Magnitude Scale

Seismic StrengthMoment Magnitude

Effects

Ground Motion

Fire

Landslides

Liquefaction

Permanent Displacement of Land Surface

Tsunami

Earthquake Damage

Taiwan, 1999

Kobe, 1995

Nigata, 1964

Gujarat, 2001

Loa Prieta, 1989

San Fernando, 1971

Earthquake DamageGround Motion and Rock Type

Earthquake DamageGround Motion and Rock Type

Mexico City, 1985

Landslides

Guatemala, 1974

Alaska, 1964

LiquefactionCollapse of beach road

Sand blow at Oakland International Airport

Liquefaction 1989 -Loma Prieta quake

Tsunamiscaused by:

• earthquakes

• undersea landslides

• icebergs falling from glaciers

• undersea volcanic eruptions

• asteroid impacts

Tsunamis

Tsunamis

Tsunamis

Detecting Tsunamis

Deep Ocean Assessment andDeep Ocean Assessment andReporting of Tsunamis (DART)Reporting of Tsunamis (DART)

Tsunami Danger

Atlantic Coast of North AmericaAtlantic Coast of North America

Plate Tectonics

Tectonic Setting of Earthquakes

Tectonic Setting of Earthquakes

Benioff Zone

Earthquake Prediction

Earthquake Prediction

Earthquake Prediction

Earthquake Prediction

Earthquake PredictionSeismic Gaps