924 



MISCELLANEOUS GEOPHYSICAL METHODS 



[Chap. 12 



absorption (see eqs. [9-35] and [9-37]). In a stratified medium the 

 directly transmitted waves interfere with refracted and reflected waves 

 because of their path and phase difference. The ampUtude-distance curve 

 is, therefore, not uniform, as in a homogeneous medium, but shows a series 



o 20 



VERTICAL GROUND RESPONSE 



IN 



5 DISTANCES FROM VIBRATOR 



20 



25 



FREaUENCY IN CYCLES PER 



FiQ. 12-20. Resonance curves of surface soil at various distances. 



30 

 CYCLES 



35 



SECOND 



of minima and maxima. Conditions for the occurrence of minima and 

 maxima have been discussed by Koehler and Ramspeck. ^ If the surface 



«« Degebo. Verofif., 4, 1-38 (1936). 



