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8.2 Measuring Earthquakes
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8.2 Measuring Earthquakes
Earthquake Waves 8.2 Measuring Earthquakes Seismographs are instruments that record earthquake waves. Seismograms are paper records of recorded ground motion made by seismographs.
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Seismograph
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Seismogram Fastest waves Slowest waves and most destructive
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8.2 Measuring Earthquakes
3 kinds of waves • P waves - Are push-pull waves that push (compress) and pull (expand) in the direction that the waves travel - Travel through solids, liquids, and gases - Have the greatest velocity of all earthquake waves “P waves move through the entire earth- crust, mantle, and core) like a slinky”
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8.2 Measuring Earthquakes
Earthquake Waves 8.2 Measuring Earthquakes • S waves Seismic waves that travel along Earth’s outer layer - Shake particles at right angles to the direction that they travel - Travel only through solids - Slower velocity than P waves “S waves move through the ground like a rope”
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Seismic Waves Paths Through the Earth
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8.2 Measuring Earthquakes
Locating an Earthquake How far is your location from the epicenter? 8.2 Measuring Earthquakes • Distance from you to epicenter is found by the measuring difference in the arrival times between P and S waves.
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Locating an Earthquake
3 seismographs are required to correctly locate the epicenter of an earthquake Epicenter is located where three circles intersect
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8.2 Measuring Earthquakes
Momentum Magnitude • Moment magnitude is the most widely used measurement for earthquakes Estimates the energy released by earthquakes. • Measures very large earthquakes
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Earthquake Magnitudes
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Some Notable Earthquakes
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Modern Earthquakes 7.2 Turkey in 2011 572 deaths
9.0 Japan in deaths
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