Gate_2017_23
23) The Percentage increase in P-wave Velocity (km/sec) across the Mohorovicic discontinuity from the lower crust to the upper mantle beneath a carton is approximately__________(%).
(Thanks to Chandrasekhar, ANU)
Solution:
As we all know the P-wave Velocities crust and mantle are as follows
Upper crust—5.6 km/sec
Lower crust-6.29 km/sec
Upper mantle-8 km/sec
The difference in the P-wave velocity between lower crust and upper mantle is
=8-6.29
= 1.71 km/sec
The percentage of this difference across the moho discontinuity is
= 1.71*100/8
=0.21375*100
=21.375%
Extra information:
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The Upper Crust is also called Granitic layer and the P and S waves are called $P_g and S_g$ waves
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The lower crust is also called Basaltic layer and the P and S waves are called $ P^* and S^*$ waves
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The P- wave in the Upper mantle is called the Head Wave which is denoted by $P_n$ wave.
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