著者

岸尾 政弘 山川 宜男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.22, no.3, pp.219-234, 1969-11-30 (Released:2010-03-11)

参考文献数

27

被引用文献数

1 1

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The precision and accuracy of locations of hypocenters of the earthquake off Tokachi of 16 May 1968 and its aftershocks are discussed mainly based on the comparison between both data determined by JMA and USCGS.USCGS epicenters are generally on the continental side of JMA epicenters. The average distance of both JMA and USCGS epicenters of each shock is 26.4km. However there are systematic differences between the JMA-USCGS epicenter deviation of aftershocks north of the mainshock and those of aftershocks south of the mainshock. The USCGS epicenters of northern aftershocks are deviated to north-west direction from the JMA epicenter while USCGS epicenters of southern aftershocks are deviated to west direction from the JMA epicenter.Focal depths of USCGS hypocenters are a little deeper than those of JMA hypocenters. 40% of JMA hypocenters and 80% of USCGS hypocenters are located in the depth of 30-40km which correspond to the top layer of the mantle.Slight differences of b-values in the magnitude-frequency relations are observed among aftershockes in the northern area (around the epicenter of the greatest aftershock), those in the middle area (around the epicenter of the main shock) and those in the southern area (around the epicenter of the second greatest aftershock).The geophysical significance of the above results is briefly discussed.