1969 年 9 月上高地における地震観測

概要

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On August 31, 1969, several earthquakes were felt at Kamikochi, Azumi Village, Nagano Prefecture. Kamikochi is situated at about 4-6 km east of the active volcano Yakedake. In order to investigate the relation between seismic activity near Kamikochi and volcanic activity of the Yakedake, we set up a temporary seismographic network by multipartite method. The observation was carried out during three weeks from September 5, 1969. Hypocenters were determined for 100 earthquakes on the basis of the arrival time of P waves and S-P. Epicenters were located in a limited area near Roppyaku-san which is about 7 km east of the Yakedake. Direction of horizontal maximum pressure which was estimated from the distribution of initial motion of P waves was found to be consistent with the regional stress field. The Yakedake showed no unusual surface manifestation during the present seismic events.
1970-04-01