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EarthquakesEarthquakes
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Earthquakes Result from StressWhat is an Earthquake?–Definition :
Shaking of a crust by a release of energy– Results :
1. Explosions, fires, broken sewage lines and water mains. Unstable roads, railroads, runways.
2. Tsunamis
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Tsunami:Tsunami: Giant ocean wave generated by an earthquake whose epicenter is on the ocean floor.
(computer generated photo)
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Causes of EarthquakesElastic – rebound theory –Definition :
When stress overcomes friction, sudden movement occurs and a snap forward occurs.
This is followed by a rebound or snap back.
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TerminologyFocus :– Where earthquakes
actually occur below the surface
Epicenter : – Point on earth’s surface directly above focus
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Magnitude vs. IntensityMagnitude–Definition:
The amount of energy released by an earthquake.
Intensity–Definition:
The amount of damage caused by an earthquake.
• Intensity: Mercalli Scale Magnitude: Richter Scale
-Scale 1- 12 -Scale 1- 10 1= no damage 30 times more energy as you 12= total destruction go up the scale
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Earthquake WavesKinds of wave motions– P Waves
Primary (compressional) wavesCan travel through any materials (solid, liquid, gas)Back and forth wavesTwice as fast as S waves
– S WavesSecondary waves Side to side wavesCan travel through solids only
– L WavesSurface wavesSlowest moving wavesCause the most damage
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Seismograph: Instrument used to detect and record vibrations from earthquakes.Seismograph: Instrument used to detect and record vibrations from earthquakes.
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Seismogram: Record of an event from seismograph
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Lag Time: Since P waves travel faster than S waves, scientists determine distance to the epicenter by analyzing the difference in arrival times.
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Lag Time:The longer the lag time between the
arrival of the P-waves and the arrival of the S-waves, the farther away the earthquake occurred.
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Locating the epicenterLocating the epicenter
Triangulate between3 or more seismograph stations
Where the circles Intersect = an
epicenter