Earthquakes

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Earthquakes
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What is an earthquake?

• Used to describe both sudden slip on a fault, and
  the resulting ground shaking and radiated seismic
  energy caused by the slip
• Caused by volcanic or magmatic activity,
• Caused by other sudden stress changes in the
  earth.

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Three Types of Faults
Strike-Slip
Thrust
Normal
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What causes earthquakes?

• Tectonic plates move past each other causing
  stress. Stress causes the rock to deform
• Plastic deformation does not cause earthquakes
• Elastic deformation rock stretches then reaches
  a breaking point, releasing energy.

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Elastic Rebound deformed rock goes back to its
original shape
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Focus point inside the Earth where an
earthquake beginsEpicenter point on Earths
surface above focus
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How Seismographs Work
the pendulum remains fixed as the ground moves
beneath it
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Typical Seismogram
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt
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Primary Waves (P Waves)

• A type of seismic wave that push and pulls the
  ground
• The first wave to arrive at an earthquake

http//daphne.meccahosting.com/a0000e89/insideear
th2.htm
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Secondary Waves (S Waves)

• A type of seismic wave that moves the ground up
  and down or side to side

http//daphne.meccahosting.com/a0000e89/insideear
th2.htm
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Comparing Seismic Waves
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Surface Waves

• Move along the Earths surface
• Produces motion in the upper crust
• Motion can be up and down
• Motion can be around
• Motion can be back and forth
• Travel more slowly than S and P waves
• More destructive

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How do scientists calculate how far a location is
from the epicenter of an earthquake?

• Scientists calculate the difference between
  arrival times of the P waves and S waves
• The further away an earthquake is, the greater
  the time between the arrival of the P waves and
  the S waves

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Locating Earthquakes
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Locating Earthquakes
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Locating Earthquakes
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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How are Earthquakes Measured? Richter Scale
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How are Earthquakes Measured? Mercalli Intensity
Scale
Click Link for Interactive Demo
http//elearning.niu.edu/simulations/images/S_port
folio/Mercalli/Mercalli_Scale.swf
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Earthquake Waves Earths Interior
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Seismic Waves in the Earth
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Tsunamis
http//www.uwgb.edu/dutchs/EarthSC-102VisualsIndex
.HTM
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Formation of a tsunami
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt
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Tsunami Warning System
http//isu.indstate.edu/jspeer/EarthSky/EarthCh11
.ppt