Earthquakes
description
Transcript of Earthquakes
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Earthquakes
Liz LaRosa http://www.middleschoolscience.com 2009 for my 7th grade science class 2009
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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-SlipThrust
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 begins
Epicenter – point on Earth’s surface above focus
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How Seismographs Work
http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM
the pendulum remains fixed as the ground moves beneath it
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Typical Seismogram
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
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Primary Waves (P Waves)
• A type of seismic wave that compresses and expands the ground
• The first wave to arrive at an earthquake
http://daphne.meccahosting.com/~a0000e89/insideearth2.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/insideearth2.htm
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Comparing Seismic Waves
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Surface Waves
• Move along the Earth’s 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_portfolio/Mercalli/Mercalli_Scale.swf
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Earthquake Waves & Earth’s 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/Earth&Sky/EarthCh11.ppt
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Tsunami Warning System
http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt