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Earthquakes

Earthquakes. What is an earthquake?. Definition-An earthquake is a vibration within earth caused by the movement of rock. Focus and Epicenters. focus - point underground where rock movement occurs that triggers an earthquake epicenter - point on Earth's surface directly above the focus.

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Earthquakes

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  1. Earthquakes

  2. What is an earthquake? • Definition-An earthquake is a vibration within earth caused by the movement of rock.

  3. Focus and Epicenters focus- point underground where rock movement occurs that triggers an earthquake epicenter- point on Earth's surface directly above the focus

  4. Location of Earthquakes

  5. Seismic Waves Waves sent through earth as an earthquake occurs are: • A) primary waves • B) secondary waves • C) surface waves

  6. P waves – Primary Waves • First to arrive at the epicenter • Travel through solids and liquids • Movement is like an accordion View movement: http://www.wwnorton.com/college/geo/egeo/flash/8_2.swf http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

  7. S waves- secondary waves • Travel only through solids • Movement is up and down View: http://www.wwnorton.com/college/geo/egeo/flash/8_2.swf http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

  8. Surface waves • Occur on earth’s surface when P and S waves arrive there. • Cause the most destruction View http://www.pbs.org/wnet/savageearth/earthquakes/index.html http://www-rohan.sdsu.edu/~rmellors/lab8/l8rwav2.htm

  9. Seismic Waves animation • http://www.phschool.com/webcodes10/index.cfm?wcprefix=cfp&wcsuffix=1022&fuseaction=home.gotoWebCode&x=10&y=11

  10. Dangers of Earthquakes • Groundshaking is one danger of earthquakes. The strongest groundshaking occurs at the epicenter of the quake. • Groundshaking is not the only hazard people face during earthquakes. They can also trigger landslides. A landslide occurs when rain soaked soil is pulled down a slope. It can cover highways and buildings in mud. In 1692, the town of Port Royal, Jamaica, slid into the sea and came to rest 50 feet below the surface. • Another hazard is liquefaction. This happens when loose, moist soil or sand is shaken so hard that individual grains separate, turning the earth into a soft, fluid slurry that can swallow entire buildings

  11. More dangers of earthquakes • tsunamis- large waves created by earthquake vibrations under the ocean • View: http://www.pep.bc.ca/tsunamis/causes_2.htm

  12. Measuring Earthquakes two approaches to measuring earthquakes: • intensity-measure of earthquake effects on people/structures (Mercalli Scale) • magnitude-amount of energy released by earthquake (Richter Scale, Moment Magnitude Scale)

  13. Measuring earthquakes’ magnitude • Richter Scale- used to measure small earthquakes that are nearby. • Uses a seismograph. • View here: http://www.wwnorton.com/college/geo/egeo/flash/8_3.swf

  14. Moment Magnitude Scale • Measures all earthquakes regardless of size or location. • Rates earthquakes from 1-12 with 12 being the largest • measures the total amount of energy released by an earthquake and takes the amount of damage into account

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