CYCLONIC MICROSEISMS GENERATED IN THE WESTERN NORTH ATLANTIC OCEAN

Abstract

Nearly all the microseism storms generated by extra-tropical cyclones in the western North Atlantic during the fall and winter seasons of 1948?49 and 1949?50 have been studied, together with some storms that occurred during the 1950?51 fall-winter. Seismograms from a number of east-coast stations and Bermuda were examined for each storm. Each of the microseism storms has been correlated with a particular marine atmospheric disturbance. The period of the microseisms appears to be a function of the depth of water in the generating area, and the regularity of the microseisms appears to be a function of the uniformity of depth in the generating area. Consequently, the position and nature of marine disturbances often can be estimated from the nature of the recorded microseisms. All the evidence on origin tends to negate ocean swell, standing waves produced by interference of ocean swell, and surf as mechanisms producing the observed microseisms. The study suggests atmospheric pulsations, resulting from turbulence or instability, to be at the root of microseism origin. Anomalies of propagation of hurricane microseims suggest the existence of a zone or surface of discontinuity along at least a portion of the outer margin of the east-coast continental shelf.