9_Earthquakes[1]

9_Earthquakes[1] - Earthquakes Earthquakes What are they?...

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1 Earthquakes Earthquakes • What are they? • How do we measure them? Where do they occur? • Where do they occur? • How do they effect us? • Can we predict them? How? What is an earthquake? • Shaking of the ground initiated by a sudden release of energy • The energy radiates as seismic waves that travel within earth and onto the surface Large seismic event result in observable ground motion Small events can be detected by instruments • This energy release can be caused by a variety of factors:
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2 Causes of earthquakes • The main cause of earthquakes is rock yielding to stresses in the earth’s crust – source of stress? why is energy release instantaneous? – why is energy release instantaneous? • Fault-related earthquakes – earthquake event makes the fault – or earthquake occurs along an existing fault Fault-related earthquake
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3 Stress is applied Strain builds up causing Elastic-Rebound Theory causing deformation Rocks break and rebound to former Undeformed shape Displacement, and movement Along Fault occurs Displacement is the amount of movement along a fault plane
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4 Displacement is the amount of movement along a fault plane Number of earthquakes • 100,000’s – 1,000,000’s of earthquakes occur each year, but, the vast majority (95 % +) are too small to be felt by humans • How many this week? – Worldwide = M4.0+; US = M2.5+
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Causes of earthquakes • 100,000’s – 1,000,000’s of earthquakes occur each year, but, the vast majority (95 % +) are too small to be felt by humans • Other causes? http://earthquake.usgs.gov/
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This note was uploaded on 05/15/2008 for the course GEOL 101 taught by Professor Kendall during the Spring '07 term at Clemson.

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9_Earthquakes[1] - Earthquakes Earthquakes What are they?...

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