Storm and Surf Microseisms 



103 



Washington) by about two days, but they 

 usually coincided approximately with the high- 

 est breakers and ocean waves recorded at or 

 observed at three points in Southern California. 

 For an example, see Fig. 1A. 



Microseisms traveling along the mountain 

 chains and fault systems which follow the 

 Pacific coast, decreased rather rapidly along 

 their paths. In some instances these "bar- 

 riers" reduce large microseismic maxima re- 

 corded at some stations to practically normal 

 size while the seismic waves travel for a few 



hundred miles in the geologically disturbed 

 area. 



The periods of the ocean waves and those 

 of the microseisms usually showed no parallel- 

 ism (Fig. IB) ; to the contrary, the microseisms 

 usually reached their largest periods at about 

 the time of the maximum amplitudes, while 

 the ocean waves frequently exhibited relatively 

 short periods when their amplitudes were large. 

 This is a consequence of the well-known fact 

 that the periods of ocean waves usually increase 

 with the distance from the source. 



Figure 6 



