Energy Sources of Microseisms in Sweden

Microseisms in Scandinavia have been so fully investigated anddiscussed from various points of view by Bàtli in a number of papera(1949, 1951a, 1951b, 1951c, 1953 and 1962) that we can hardlv addanything by the sanie method. There is another statistica! investigationby Zàtopek (1961) about the relation between the positions ofenergy sources over the northernmost Atlantic Ocean and the microseismactivity of Europe, including Scandinavia.The present author made other kinds of investigations of the relationbetween microseismic storms and the passage of c.yclones, typhoons orcold fronts across or around Japan during I.G.Y., using data obtainedat eleven stations along the Japanese Islands (Santo 1959a, 1959b and1960). The writer found that microseisms with periods of 4 to 10seconds are produced by standing ocean waves, due to interferencebetween incident and reflected swells at some steep coasts.Ile had favourable opportunity to investigate the microseisms atKiruna und Uppsala, Sweden, by means of the sanie method. Theinaili purpose of the present worlc is to investigate the validity of theconclusion found for Japan.The materiate used were the Z component ainplitudes and periodsof microseisms recorded at Kiruna by Galitzin seismographs and atUppsala by Benioff long-period seismographs during I.G.Y. The weathermaps published by the Swedish Meteorologica! and Hydrological Instituteof Stockholm were used in order to find the energy sources of microseismicstorms. As the weather maps used show the situation onlyonce a day, tlie energy sources related to microseismic storms of shorterduration may sometimes be missing in the present investigation