Wednesday, January 6, 2010

How do you figure out this geology problem?

P-wave velocity is 8 km/sec. S-wave velocity is 3 km/sec. If the P-wave arrives at a seismographic station 5 seconds ahead of the S-wave, how far away was the earthquake?





a. 15 km


b. 24 km


c. 30 km


d. 48 kmHow do you figure out this geology problem?
Figure it out. Here's an easy way:





at t0, the distance both P and S waves have travelled is 0.


at t1 (1 sec), P = 8 km, S is 3 km


at t2 (2 sec), P = 16 km, S = 6 km


at t3 (3 sec), p = 24 km, S = 9 km





Just keep doing that until the difference in the distances is 15 km, and that will be your answer.

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