Earthquakes are essentially sound waves-called seismic waves-traveling through the earth. Because the earth is solid, it can support both longitudinal and transverse seismic waves. The speed of longitudinal waves, called P waves, is 8000 m/s. Transverse waves, called S waves, travel at a slower 4500 m/s. A seismograph records the two waves from a distant earthquake. If the S wave arrives 2.0 min after the P wave, how far away was the earthquake?You can assume that the waves travel in straight lines, although actual seismic waves follow more complex routes.

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Alaina Mcintosh · Accepted Answer

From the time delay, we can write:      t          s        −      t          p        =  △  tKnowing that   t  =      d    v  , we rewrite the formula as      d          v              S              −      d          v              P              =  d  (      1          v              P              −      1          v              S              )  =  △  tFrom this we can find the distance to be  d  =                    v                  S                            v                  P                                    v                  P                    −              v                  S                      △  t  =            8000      ∗      4500              8000      −      4500        ∗  120  =  1230  k  mResult:1230 km

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