地震による放出エネルギーの深さ別分布について(I)

The world-wide and regional earthquake energy release in relation to focal depth are calculated based on the data of the Preliminary Determination of Epicenters (PDE) of USCGS for the period of January 1963-June 1966. Number of earthquakes are listed according to their magnitudes and depths, with 0.5 magnitude unit and 30 km depth range classifications. Three apparent discontinuities of frequency at 30-60, 270-300 and 420-480km depths allow us to classify the earthquakes into the shallow (<60 km), intermediate (<300 km), transient (<450 km) and deep (≥450 km) focus groups. Energy depth frequency is calculated for various different seismic regions which show, firstly, very clear regional characteristics with minima at the depth of 100-200 km corresponding to the asthenosphere low velocity layer. The second minima, found at the depth of 210-330 km in both Kamchatka-Kuril Islands and Japan-Bonin Islands Regions, are generally at the depth of 300-450km in the other seismic regions separating the intermediate and deep focus earthquakes. The shape of the energydepth curve is interpreted in terms of the structure, physical conditions and intensity of the strain accumulation.USCGSのPDE (Preliminary Determination of Epicenters)にもとづいて1963年1月から1966年6月までの3.5年間に発生した地震による放出エネルギーの深さ別分布を,世界全体ならびに地域別にしらべた.その結果世界の平均としては地震による放出エネルギーの分布は震源の深さによつて, Shallow (<60km), Intermediate (<300km), Transient (