SECT. 5] 



MICKOSEISMS 



705 



noted by other workers. Dinger and Fisher (1955) found such a relation at the 

 island of Guam, when both high waves and high microseisms occurred together. 

 Inouye (1954) compared microseisms at Tokyo with sea waves recorded at 

 Jogashima and found similar results. Gutenberg (1952) found a close correlation 

 between the amplitude of microseisms at Santa Clara, California, and wave 

 heights at Ellwood, California. 



Wave spectra 



Microseism spectra 



Wave spectra 



Microseism spectra 



13 Marcti 

 1900 



14 March 

 500 



1500 



^.^4tH'^Uv,-^ _J;UMi 



!''''!' '"1" 

 10 15 20 



5 7.5 10 



Period in seconds 



Period in seconds 



Fig. 5. Simultaneous wave and microseism spectra. (After Darbyshire, 1950.) 



Work on the eastern coast of the United States has not entirely supported 

 this relation nor the wave interference theory. The work in this area has been 

 carried out mainly at the Lamont Observatory by W. L. Donn and others. 

 Donn (1951, 1951a, 1952, 1952a) finds that microseisms are only formed when 

 storms cross the American continental shelf and that the period of the micro- 

 seisms depends on the depth of water in the storm area. These observations 

 support a theory that microseisms are formed by a cold front crossing the shelf 



