著者

Hamada Kazuo Hagiwara Takahiro

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.44, no.3, pp.1239-1268, 1967-01-30

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The first high sensitivity tripatite observation was made at Hoshina, Nagano Prefecture in the period from October 31 to December 18, 1965 and the observational result has been reported as the first report. This paper is the report of the result of the second observation by the same method in the same region, observation starting again on February 20, 1966 after an interruption of sixty days and continuing through the end of June, 1966. This paper is confined to the result obtained in the period from February 20 to June 20, 1966. In the first observation, we have found that the locations of the seismic foci determined by our tripartite method were perceptibly accurate. Therefore, in the second observation, the sensitivity of the instruments was raised higher than the first observation and we registered a large number of ultra-micro earthquakes. The recorded earthquakes were analyzed and the locations of the seismic foci were determined immediately after the observation. Thus, the second observation by our tripartite method was used as a lookout in the area of Matsushiro Earthquakes. For that reason the work of analysis of the earthquakes including the calculation by an electronic computer was consolidated thus raising the efficiency of the work. As regards the methods of observation and determination of the seismic foci, we used the same methods as described in the first report, so we omit description of the methods in this paper reporting only the results of the observation.第1回の高感度3点方式による松代地震の観測は, 1965年10月31日から12月18日にかけて行われ,その結果を第1報として報告した.この報告は同じ地域で同じ方法による地震観測の第2報である.第2回の観測は第1回観測から60日の間を置いて1966年2月20日から再開され6月末現在なお継続中である.この報告は1966年2月20日から6月20日までの観測結果についてのものである.第1回観測結果から,われわれの3点方式によって定めた震源の位置が比較的良く定まっていることがわかった.そこで今回はもう少し感度を上げ,短時間に多くの極微小地震を観測し,直ちに解析を行ない,主に震源の位置を調べて松代地震地域における1つの監視として役立てることにした.そのために又電子計算機を中心とする解析作業を整備し,能率化して対処した.