120 



Symposium on Microseisms 



have used the numerical values a/b = \/3, 

 b/c = 2 andp/p 1= 0.4). 



Figure 2 



With the exception of the first mode each 

 curve starts at sin 3=1 an d approaches sin 

 3 = b/c asymptotically. The curve of the first 

 mode shows two peculiarities : 



if h = <t> the equation N = changes into the 

 simple Rayleigh equation for the suboceanic 

 medium 



b2 



cos 2 2(3 + 4 sin 2 (3 cos 3 (- sin 2 B) 



a 2 



\\ l A - o 



with the root sin 3 = b/S,, where S, = the 

 velocity of Rayleigh waves. At smaller values 

 of sin /3 (in fig. 2 for sin B < 1.0788) the equa- 

 tion N = yields a negative value of vh/b. 



In the second place: if h = oo the equa- 

 tion changes into the equation for Stoneley 

 waves in the two semi-infinite media (water 

 and suboceanic rock) : 



:os 2 2(3 + 4 sin 2 (3 



:os 6 I 



b 2 — \y 2 p /b 



— - sin 2 (3 = 2i — 



1 (l5-« in2 0"(^- Sln2p )"'" 



