chapter11

# Chapter11 - Key Terms and Concepts Earthquakes elastic rebound theory foreshocks and aftershocks Types of seismic waves Surface(Rayleigh and Love

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Key Terms and Concepts Earthquakes: elastic rebound theory, foreshocks and aftershocks Types of seismic waves Surface (Rayleigh and Love) Body (P and S) Equations for velocity of waves Locating EQ epicenters (directly above focus) Distribution of EQ foci and relation to plate boundaries Richter magnitude scale Earthquake Destruction (ground vibrations, tsunamis, landslides, liquifaction, fires) Prediction

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What is an earthquake? earthquake sudden release of energy source or focus usually along faults energy radiates in all directions elastic waves recorded by instruments around the world Arrival time, first motion Amplitude (A), frequency(f), wavelength ) , period (P), P = 1/f     λ  = speed/f
What is an earthquake? Elastic rebound Rocks on both sides of an existing fault are deformed by tectonic stresses Rocks deform (strain) and store elastic energy Frictional resistance holding the rocks together is overcome Slippage at the weakest point (the focus) occurs Vibrations (earthquakes) occur as the deformed rock “springs back” to its original shape ( elastic rebound )

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What is an earthquake? Foreshocks and aftershocks Adjustments that follow a major earthquake often generate smaller earthquakes called aftershocks Small earthquakes, called foreshocks , often precede a major earthquake by days or, in some cases, by as much as several years
San Andreas:  An active  earthquake zone San Andreas is the most studied fault system in the world Displacement occurs along discrete segments 100 to 200 kilometers long Some portions exhibit slow, gradual displacement known as fault creep Other segments regularly slip producing small earthquakes ( seismic portion)

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San Andreas:  An active  earthquake zone Displacements along the San Andreas fault Still other segments store elastic energy for hundreds of years before rupturing in great earthquakes Process described as stick-slip motion Great earthquakes should occur about every 50 to 200 years along these sections
Seismology The study of earthquake waves, seismology , dates back almost 2000 years to

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## This note was uploaded on 03/27/2008 for the course GEOL 101 taught by Professor Olinsky during the Fall '08 term at Texas A&M.

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Chapter11 - Key Terms and Concepts Earthquakes elastic rebound theory foreshocks and aftershocks Types of seismic waves Surface(Rayleigh and Love

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