Amplitude Distribution of Storm Microseisms 



29 



Figure 9. Micro-ratio chart between Jacksonville and Cherry Point 



find their intensity. Amplitude charts, there- 

 fore, are very important in storm forecasting. 

 The micro-ratio technique mentioned briefly 

 before, is still another step forward in the 

 tracking of severe storms. This technique can 

 be used independently of the amplitude charts, 

 but the two together can give all the informa- 

 tion necessary for detecting and tracking of a 

 storm and for finding its intensity. 



The technique involved in the construc- 

 tion of micro-ratio charts is based upon the 

 observed fact that a storm at any specific place 

 will cause the amplitude of the microseisms at 

 two recording stations to be in a definite ratio 



to each other regardless of the intensity of the 

 storm, the geologic formation through which 

 the microseisms pass, or the distance of the 

 storm from the station. It is important to 

 note that this technique does not presuppose 

 anything concerning the method of generation 

 or of propagation of microseisms, since one 

 hurricane at any particular place will generate 

 and transmit microseisms in the same manner 

 as any other hurricane in the same place. For 

 example, when the first storm of 1950 was lo- 

 cated at 39 = N and 70 C W, the ratio of the mi- 

 croseismic amplitudes between Cherry Point 

 and Jacksonville was 2.5. The fourth storm 

 of the year, one of less intensity, passed over 



