(I have the answer I just need to see how it\'s done:d= = 900 km) 6 Earthquakes

Question

(I have the answer I just need to see how it's done:d= = 900 km)

6 Earthquakes generate two types of waves, which travel through the earth: (1) primary, or P, waves are longitudinal pressure waves that have the greater speed (about 5 km/s in the crust) and are therefore the first to be felt at some distance from the center of the earthquake, and (2) secondary, or S, waves are trans- verse, shear waves that are somewhat slower (v ~ 3 km/s). The location of the earthquake can be determined by recording the arrival times for these waves on seismographs at various locations. Suppose an S wave is recorded 2 min after a P wave. About how far away from the seismograph is the earth- quake's center?

Explanation / Answer

say the epicenter distance is "d" in km away

so here 3 km/s = 3000 m/s

and 5 km/s = 5000 m/s

time 2 min = 120 sec

for the transvese wave d = 3000 ( t + 120 )

for the longitudinal wave d = 5000 t

now equating both

3000 ( t + 120 ) = 5000 t

3 ( t + 120 ) = 5 t

3 t + 360 = 5t

2t = 360

t = 180 sec

d = 5000 t

d = 5000 X 180

d = 900000 m

or

d = 900 km

so answer is 900 km correct.

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