Amplitude Distribution of Storm Microseisms 



35 



the peak the period was about 8 sec. at Sitka 

 and 8.5 sec. elsewhere including Victoria, 

 Ukiah, and Tucson, but not including Pasa- 

 dena. There was no evidence of an 8 + sec. 

 period at Honolulu at this time. 



Again it may be assumed that the micro- 

 seisms during the peak activity at all stations 

 where 8 + sec. periods were dominant had a 

 common source area, and that in this case the 



area was near the west coast, more specifically 

 nearer Sitka than Victoria, for instance. 



This series of records indicates that these 

 microseisms may undergo a slight increase in 

 period during the first few hundred kilometers 

 of their journey, but thereafter they continue 

 across the continent, including the western 

 mountain systems, with no material change in 

 period. Since Berkeley records microseisms 



Figure 3. Weather chart of North America for 15 January 1950 at 18h 30m GCT showing a storm 

 moving off the coast of labrador which is believed responsible for the generation of the micro- 

 seisms shown in figure 2, courtesy of U. S. Weather Bureau. 



