Earthquakes

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Lecture 19 Earthquakes
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Lecture Outline
I Definitions II Properties A) Focus and
Epicenter B) Seismic Waves i. Body
Waves ii. Surface Waves C) Strength i. I
ntensity ii. Magnitude III Effects IV Plate
Tectonics and Earthquakes A) Plate
Boundaries i. Divergent ii. Convergent
iii. Transform B) Subduction Angle V Conclusions
Lecture 19 i
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Definitions
earthquake - the vibration felt when energy is
released
abruptly by the sudden displacement of rock
along faults within the Earth's crust
fault - fracture or fracture zone
along which there has
been displacement of the sides relative to
one another
fault line - the intersection of a fault with
the surface of the
Earth, or the trace of a fault on a surface of
reference
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Tectonic Deformation Elastic Rebound
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Tectonic Deformation Elastic Rebound
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Properties

• Focus
• Epicenter
• Seismic Waves
• Stength

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Seismic Waves

• Body Waves

• P (primary) Waves
• S (secondary) Waves

• Surface Waves

• Love Waves
• Rayleigh Waves

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Seismic WavesBody Waves
P (Primary)Waves
S (Secondary)Waves
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Seismic WavesBody Waves - Refraction
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Seismic WavesBody Waves - Pathways
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Seismic WavesSurface Waves
Rayleigh Waves
Love Waves
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Detecting Seismic Waves
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Detecting Seismic Waves
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Detecting Seismic Waves
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Detecting Seismic Waves
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Detecting Seismic Waves Finding Epicenter
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Detecting Seismic Waves
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Detecting Seismic Waves First Motion Analysis
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Detecting Seismic Waves First Motion Analysis -
Strike Slip Faults
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Seismic Strength

• Mercalli Intensity Scale
• Richter Scale (Magnitude)
• Moment Magnitude

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Seismic Strength Intensity

• Measure of severity of ground shaking
• Decreases with distance from focus
• Shallow focus (lt30km) gt deep focus (gt100km)
• Greater on unconsolidated sediment than on bedrock

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Seismic Strength Modified Mercalli Intensity Scale
1811 New Madrid Earthquake 1906 San Francisco
Earthquake
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Seismic Strength Richter Magnitude Scale
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Seismic Strength Richter Magnitude Scale
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Seismic Strength Moment Magnitude
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Effects

• Ground Motion
• Fire
• Landslides
• Liquefaction
• Permanent Displacement of Land Surface
• Tsunami

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Earthquake Damage
Kobe, 1995
Loa Prieta, 1989
Nigata, 1964
Taiwan, 1999
Gujarat, 2001
San Fernando, 1971
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Earthquake Damage Ground Motion and Rock Type
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Earthquake Damage Ground Motion and Rock Type
Mexico City, 1985
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Landslides
Guatemala, 1974
Alaska, 1964
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Liquefaction
Collapse of beach road
Liquefaction 1989 -Loma Prieta quake
Sand blow at Oakland International Airport
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Tsunamis

• caused by
• earthquakes
• undersea landslides
• icebergs falling from glaciers
• undersea volcanic eruptions
• asteroid impacts

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Tsunamis
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Tsunamis
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Tsunamis
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Detecting Tsunamis
Deep Ocean Assessment and Reporting of Tsunamis
(DART)
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Tsunami Danger
Atlantic Coast of North America
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Plate Tectonics
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Tectonic Setting of Earthquakes
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Tectonic Setting of Earthquakes
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Benioff Zone
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Earthquake Prediction
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Earthquake Prediction
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Earthquake Prediction
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Earthquake Prediction
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Earthquake Prediction Seismic Gaps