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seismology earthquake Seismic waves

seismology earthquake Seismic waves. The study of earthquakes Occur along fault lines The shaking and trembling that results from movement of rock beneath the Earth’s surface Most too small to notice Caused by plate movement Waves of energy that travel through the Earth

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seismology earthquake Seismic waves

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  1. seismology earthquake Seismic waves The study of earthquakes Occur along fault lines The shaking and trembling that results from movement of rock beneath the Earth’s surface Most too small to notice Caused by plate movement Waves of energy that travel through the Earth Similar to sound waves

  2. Locating Earthquakes Epicenter focus The point on the Earth’s surface directly above the focus of an EQ The point inside the Earth where the EQ begins

  3. P- waves http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm?chapter_no=visualization S-waves Surface Waves Primary wave 1st to arrive Travels through liquid, solid & gas Squeezing & stretching like accordian Secondary wave Second to arrive Travels like an “s” Travels through solids & gases, not liquids Moves slower than P & S waves Produces severe ground movement Only on surface, up & down & in circles

  4. Measuring Magnitude Modified Mercalli Scale Rates the amount of shaking from the earthquake Uses peoples observations Useful in areas w/o many instruments Richter scale Rates on size of EQ waves recorded by seismographs Quakes get exponentially larger Moment Magnitude Rates total energy an EQ releases Usually the number that is quoted on the news Each point is approximately 32 x more energy Below magnitude 5 not much damage Above 6 can cause great damage Above 8 is rare

  5. Locating the Epicenter Geologists use seismic waves to locate the epicenter Using P & S waves Read the distance of the seismic wave arrival 3 seismograms from 3 locations for the same EQ Draw a circle of using the distance as a radius Where 3 circles intersect = epicenter

  6. Locating Earthquakes Seismograph The instrument that is used to track EQs & record seismic waves The tracing motion is called a seismogram Used to determine start time Used to find where it started Seismic waves cause the drum to vibrate – and a pen records the vibrations The paper moves and the pen stays in place Weight of seismograph resists moving Must be very strong movement to trigger Seismograms reveal patterns of earthquakes around the world, revealing patterns

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