25.昭和11年2月21日河内大和強震調査報告 [in Japanese] 25.The Kawati-Yamato Earthquake of February 21st, 1936. [in Japanese]
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The earthquake which shook Osaka and the surrounding country on Feb. 21st, 1936, has, from the point of view of the damage caused thereby, to be accounted the severest earthquake which has visited the central Japan since the destructive Tango earthquake of 1927. Although the intensity of the shock was not so great within the epicentral area it caused great panic among the citizen of Osaka. It is clear that the shuck did not reach an intensity comparable to that experienced in some of the earthquakes that have affected Japan, notably the Kwanto, Tango, Idu earthquakes. The intensity has been estimated to be V on the intensity scale generally used in Japan, the second figure on that scale. In Fig.1 the area over which the shock reached this intensity is shown by shaded boundary. It is reported that 77 aftershocks were recorded during the first 24hours after the earthquake, of which 22 were sensible, But, the aftershocks rapidly decreased in number from the next 24hours. The observations of the aftershocks were begun on Feb, 22 at 2 A.M. Three portable seismographs and two acceleration seismographs were installed at the stations as shown in Fig.1, In Osaka the acceleration seismographs were installed at two places for the purpose of the simultaneous observation. After one or two earthquakes were recorded at these stations the instruments were installed at other places. In doing so the observations were made at five stations, In five aftershocks which occurred in two weeks following the big earthquake, the positions of the seismic foci could be determined Fig.1, The focal depths of these shocks were less than 10km. The constant factor, k, in the formula, D=kt, which is used in computing the focal distance, D(in km), by means of the duration of the preliminary tremors, t(in sec.), has been determined with result that it takes a value 6.15 in the case of the present earthquakes.
- 東京帝國大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, Tokyo Imperial University
東京帝國大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, Tokyo Imperial University 14(2), 285-289, 1936-06-05