Earthquakes generate sound waves inside the earth. Unlike a gas, the earth can experience both transverse (S) and longitudinal (P) sound waves. Typically the speed of the S wave is about $$4.0 km s^{–1}$$, and that of the P wave is $$8.0 km s^{–1}.$$ A seismograph records P and S waves from an earthquake. The first P wave arrives 4 min before the first S wave. Assuming the waves travel in a straight line, at what distance does the earthquake occur?

Asked by Pragya Singh | 1 year ago |  240

##### Solution :-

Let the speeds of S and P be v1 and v2 respectively. The time taken by the S and P waves to reach the position of the seismograph is t1 and trespectively

l = v1t1 = v2t2

The speed of S wave, v1=4.0 kms–1

The speed of P wave, v2= 8.0 kms–1

4t1 = 8t2

t1 = 2t2

The first P wave arrives 4 min before the S wave.

t1 – t2 = 4 min = 4 x 60 s = 240 s

2t– t2 = 240 s

t2 = 240 s

t1 = 2t2 = 2 x 240 = 480 s

Distance at which earthquake occur, l = v1t1 = 4 x 480 = 1920 km

Answered by Abhisek | 1 year ago

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