58 G Velocity of Propagation of an Earth quake- Wave. 



Putting fTTflo = 2^ so as to reduce the angles to circiik 

 measure, we have 



where p _ 36'6 



Now lrf.r = 2 d f* /(«)^ 



IT d p Qg-a>i« 



36 d?; 



This gives 



log * =- ^ [> cosh- 1 £ - V/3 2 - V 2 ] > 

 where # 



The velocity at the surface is 



TT 1 7T 6370 . ., , 

 U = yz = — TT, -^tt" kilometres per sec. 

 p .Ib'o bU 



= 9*1 kilometres per sec. 



The following table will give some idea of the way in 

 which the velocity changes with the depth when the above 

 equation is satisfied. 



