GEOL 106 Lecture Notes - Love Wave, Seismic Wave, Rarefaction
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31 Jan 2013
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Read ch 3: Tsunamis
Seismic Waves
-How do we find the focus of the earthquake? In other words, how far
away is the earthquake?
First we need to know what seismic waves are and how they behave
-Recall GEOL 104
-Seismic energy waves radiate out from the focus of an earthquake as
body waves
-Some body wave motion gets transferred into surface wave motion
when the body waves reach the surface
-Types of surface waves:
Love waves: move perpendicular to the direction of energy
movement
Rayleigh waves: move in circular motion
-Types of body waves:
P-Waves: push-pull (compression and rarefaction)
S-Waves: Shear
-What is the velocity of seismic waves, and what does the velocity
depend on?
Velocity of P and S waves depend on Elasticity/Density, of the
material they are moving through
-The more elastic a material is, the higher the seismic velocity
-The more dense a material is, the lower the seismic velocity
Both P and S wave velocities change when they move into a different
material
-From equation (find in text): K=compressibility modulus (stress
needed to compress the material). Mu=shear modulus (stress needed
to change the shape).
-P wave will always have higher velocity than s-wave; compare
equations to see that