昭和37年4月30日宮城県北部地震調査報告

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1. On April 30th, 1962 the northern part of Miyagi Pref. suffered a considerable earthquake. The epicenter and other data are reported by the Japan Meteorological Agency as follows (See Fig. 1.); Epicenter 141°08'E, 38°44'N Origin time 11h26m21sO Depth of focus 0 km Magnitude M = 6.4. The damage caused by this earthquake was Loss of lives 3 People injured 272 Houses completely destroyed 340 Houses half collapsed 1,114 Houses broken 30,165 Amount of damages \2,400,000,000. 2. The occurrence of earthquakes in this area is not frequent, and we can find only a few reports in the old records of earthquakes, of which the most conspicuous one is the shock of May 12th, 1900. This earthquake was located a little south of the present one and the magnitude seems to have been slightly larger. There might have been other local destructive shocks in the same area, but the poor condition of instrumental observation makes it impossible to determine the epicenters correctly. 3. The damaged area of this earthquake is the northern plain of Miyagi Pref., west of the the River Kitagami. The topography and geology of this area is classified as follows: (Cf. Figs. 2 and 3) Topography Altitude Formation and rocks near surface 1. Alluvial plain 5～20m Alluvium (sand, clay, gravel) 2. River terrace <40m Sand and gravel 3. Hill 40～90 m Pliocene (tuff, lignite, sandstone, gravel) 4. Mountain 200 m Miocene (sandstone, tuff) Permian (slate) Most of the destroyed houses were located in the former swamp area or in the alluvial plain. 4. The statistics of the damage in Miyagi Pref. were made public and are given in Table 4. 5. Field observation of the damage to houses, rail road, roads, bridges etc. is de- scribed in § 5. 6. The post card method of investigation was performed by H. Kawasumi and his colleagues and 2,000 post cards were mailed to the prefectures Akita, Yamagata, Iwate, Miyagi, Fukushima and the northern part of Tochigi. (Cf. The questionaire in Fig. 5.) The direction of earthquake sound was studied using the answers to the above questionnaire and the most probable point was determined, which point was assumed to be the source of sound. (141°05'E, 38°41'N. See Fig. 6.) The frequency function of the angle between the direction of the above determined point and that of the earthquake sound was obtained and is given in Fig. 7. Overturning of tomb stones was studied both from the field investigation and from the post card method. A similar method was applied and the center point of the directions of overturning was calculated (141°04'E, 38°41'N. Fig. 8). The rate of overturning and the acceleration estimated from this data are illustrated in Figs. 9 and 10. The data of boring done for the Furukawa City water supply was kindly presented by the municipality and the location of wells and columnar diagrams are shown in Fig. 11. 7. This investigation was carried out only by the support and the cooperation of Miyagi Prefecture, Department of Geophysics Tohoku University, Tohoku Local Bureau Ministry of Construction, and other local corporations and institutions. The authors'sincere thanks are due to them.
東京大学地震研究所,Earthquake Research Institute, University of Tokyo,地震研究所の論文
1962-11-30

著者

松田時彦
西南学院大

昭和37年4月30日宮城県北部地震調査報告

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