wave_mechanics critical_thinking Question 51
Question: An earthquake generates both transverse (S) and longitudinal (P) sound waves in the earth. The speed of S waves is about 4.5 km/s and that of P waves is about 8.0 km/s. A seismograph records P and S waves from an earthquake. The first P wave arrives 4.0 min before the first S wave. The epicenter of the earthquake is located at a distance about
[AIIMS 2003]
Options:
A) 25 km
B) 250 km
C) 2500 km
D) 5000 km
Show Answer
Answer:
Correct Answer: C
Solution:
Suppose d = distance of epicenter of Earth quake from point of observation vS = Speed of S-wave and vP = Speed of P-wave then $ d=v _{P}t _{P}=v _{S}t _{S} $ or $ 8t _{P}=4.5t _{S} $
Therefore $ t _{P}=\frac{45}{8}t _{S}, $ given that $ t _{S}-t _{P}=240 $
Therefore $ t _{S}-\frac{4.5}{8}t _{S}=240 $
Therefore $ t _{S}=\frac{240\times 8}{3.5}=548.5s $ \ $ d=v _{S}t _{S}=4.5\times 548.5 $
$ =2468.6\approx 2500km $
BETA
