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I have a very simple mental picture that earthquake waves travel like shear (transverse) waves through the earth.

a. Does the speed of this wave give any valuable information about the mechanical properties of the geological medium?

b. Can this data be used to characterize mechanical properties of the earth?

c. Can the speed of this wave be estimated by recording the time taken for the earthquake wave to reach sensors at different locations?

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Seismic waves can be transverse (shear) or longitudinal (like sound). These are called S and P waves respectively. They can indeed give lots of info about the structure of the Earth. Have a look at en.wikipedia.org/wiki/Seismic_wave to get a basic idea and come back if you have any more specific questions. –  John Rennie Oct 16 '12 at 17:38
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up vote 3 down vote accepted

First of all, Earthquakes are not necessarily transverse waves. Both transverse and longitudinal waves are there in Seismic waves. These waves depend upon both Modulus of elasticity and Density of medium. Longitudinal P-waves (primary) have properties similar to that of sound and due to their compressive & rarefactive wave motion, They reach us faster than transverse S-waves (secondary). These are the Before-socks as what we call.

It is the effect of S-waves which cause the shear fracture of the rocks (due to high amplitudes). They result of rapid sideways movement of faults thereby causing rocks to shake randomly around their hypo-center. They typically travel up to 60% of the velocity of P-waves. They necessarily require the Shear-modulus of the medium. But, they're the most destructive type of all.

All the answers for your questions are YES. 'Cause they've already been a done-deal..!

Refer Wiki for a more detailed description regarding the topic...

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Add the link on seismology en.wikipedia.org/wiki/Seismology to complete your answer. The earths interior has been mapped using seismic waves, which answers a. –  anna v Oct 16 '12 at 18:13
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