波浪はどこで脈動に変わるか? (続)

Abstract

Origin of microseisms is re-examined by using the data of I. G. Y. at Kiruna and Uppsala, Sweden.Microseisms observed at these Scandinavian stations revealed the following clear connection with the travelling courses of cyclones over the Ocean.1. A cyclone which takes such distant course as far as more than 1000km from Norwegian coast increases, without any exception, the periods but does not the amplitudes of microseisms.2. A cyclone which moves along the course approximately from 500km to 1000km far off the Norwegian coast increases both the amplitudes and periods of Scandinavian microseisms.3. Due to a small cyclone which moves near Scandinavian coast, microseisms are increased in their amplitudes only.Swells generated by a cylone gradually lose their amplitudes and gain their periods during the travelling over the Ocean. Therefore, the observed facts given above tell that the amplitudes and periods of microseisms are both completely controled by those of swells at some coast near the stations on the land.This suggestion was confirmed by comparative studies between the estimated arrival times of swells due to each distant cyclone at some coasts near the station and the beginning of long period microseisms observed.The following three facts were also observed.4. A double or a tripple cyclone over the Ocean has no effect upon microseisms.5. Microseismic wave hardly propagate over the Ocean.6. Propagation of microseismic waves is disturbed by topographical irregularity of the continent.