In order to show the general feature of seismicity in and near Japan, epicenters off earthquakes have been plotted in the maps of Japanese islands.
1) The data in 15 years from 1951 to 1965 have been made use of.
2) The epicenters of earthquakes of different depths have been plotted on the different maps.
3) The magnitudes of earthquakes are shown in the maps by the size of epicenter marks. The magnitudes of earthquakes whose foci are deeper than 60km are determined with the method proposed by the present author.
4) The epicenters of earthquakes whose magnitudes are larger than 41/2 are plotted in the maps, but it should be mentioned that the earthquakes whose epicenters can be determined without omission by the J. M. A. are those whose magnitudes are larger than 52/1-53/4.
The important results are as follows:
1) The epicenters of very shallow earthquakes are equally distributed in and near Japan.
2) The seismic activities are most remarkable in the depths from 40 to 70km. Also it is easily seen that the most active zone is in the zonal area of Pacific Ocean side north from Kwanto district.
3) The epicenters of earthquakes of intermediate depth from 70 to 300km are rather widely distributed in and near Japan, but the two rather concentrated zones, one from the Kurile islands to Bonin islands and the other from Kyushu to the Ryukyu islands, are noticed.
4) The epicenters of earthquakes whose foci are deeper than 300km are distributed according to the wellknown belts, one crossing Japan transversely to Manchuria, the other extending from Manchuria across southern Sakhalin into the Sea of Okhotsk.
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