Which of the following statements with reference to shadow zones in an event of an earthquake is/are correct?
1. Zone between 105° and 145° from epicentre was identified as the shadow zone for both P-waves and S-waves
2. The shadow zone of P-waves is much larger than that of the S-waves
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Quantrex Academy · Accepted Answer

Correct answer: A. 1 only

Seismographs located at any distance within

105^{{}^{\circ}}

from the epicentre record the arrival of both P-waves and S-waves. However, seismographs located beyond

145^{{}^{\circ}}

from the epicentre record the arrival of P-waves, but not S-waves.

Thus, the zone between

105^{{}^{\circ}}

and

145^{{}^{\circ}}

from the epicentre is identified as the shadow zone for both types of waves. Hence, statement 1 is correct.

The entire zone beyond

105^{{}^{\circ}}

does not receive S-waves. The shadow zone of S-waves is much larger than that of P-waves, covering over

40\%

of the earth's surface. Hence, statement 2 is incorrect.

Answer: 1 only

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