Earthquakes and Earth's Interior

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Earthquakes and Earth's Interior

• Shake and Bake

Geol 1301
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Part 1 What is an Earthquake?

• A vibration of the earth caused by a sudden
  release of energy, usually the result of faulting
• Sound is a similar vibration
• Earthquakes are often followed by smaller
  earthquakes called aftershocks

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Historic Effects of Earthquakes
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Earthquake Tales
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Earthquakes Today
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US Earthquake Risk
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Causes of Earth Shaking

• Earthquakes
• Magma movement
• Human activity (mining, injection)
• Faults -- stress build up and release
• Explosions
• Underground nuclear tests
• Mining explosions

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Elastic rebound theory

• Elastic Rebound Theory
• Harry Reid studied the 1906 San Francisco fault
  scarp
• Rocks bend as stress is applied and then snap
  back when they break along faults
• Rocks exhibit brittle behavior in lithosphere

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San Andreas Fault and the 1906 Earthquake
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Fault Scarp
1906 Event
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7.25 vel/dep
fence crack
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Vocabulary

• Seismology
• Focus/Hypocenter
• Epicenter
• Fault plane
• Surface rupture/fault scarp
• Magnitude (size)
• Duration

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Understanding the Earth and earthquakes

• Seismology
• Study seismic waves that travel through the
  Earth
• Requires understanding of wave propagation and
  earth and man-made processes
• Earthquakes
• Earth structure
• Nuclear explosions
• Tools
• Seismograph/Seismometer -- machine for detecting
  earthquakes
• Computers

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