posted by sarah .
Earthquakes are essentially sound waves travelling through the earth. They are called seismic waves. Because the earth is solid, it can support both longitudinal and transverse sismic waves, which travel at different speeds. The speed of longitudinal waves, called P waves, is 7707.0m/s. Transverse waves, called S waves, travel at a slower 3800.0m/s. A seismograph records the two waves from a distant earthquake. If the S wave arrives 3.82min 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.
since the distances are the same, and
distance = speed * time
then, using t as seconds,
7707t = 3800(t+229.2)
t = 222.92 s
7707*222.92 = 1718044m = 1718 km