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タイトル: Matsushiro Earthquakes Observed with a Temporary Seismographic Network : Part 4.
その他のタイトル: 臨時地震観測網による松代地震群の調査結果 : 第4報
著者: the Party for Seismographic Observation of Matsushiro Earthquakes
the Seismometrical Section
著者(別言語): 地震観測班
発行日: 1967年11月30日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第45冊第3号, 1967.11.30, pp. 887-917
抄録: The Matsushiro earthquake swarm commenced in August 1965 and continues even at present when more than a year and a half has passed since the outbreak. For the sake of convenience, we divided the activity of this earthquake swarm into four stages. The first stage of activity: This was the period from the outbreak of the earthquake swarm to February 1966, the highest peak of the activity occcurring in November 1965. The main shocks took place around Mt. Minakami, especially on its southwestern side, during this period. Shocks were not felt so frequently as later at Hoshina at that time. The second stage of activity: This began in March 1966 and continued to the beginning of June 1966. The activity at this time was most violent throughout the whole period, the area of seismic activity extending to a broader area of Matsushiro and Wakaho. In April 1966, the frequency of earthquakes reached the maximum throughout the whole period and large shocks with intensity of IV or V on the JMA scale took place frequently, inflicting some damage on dwelling houses and other constructions in this area. The third period of activity: This continued from August to October 1966. The seismic active area in this period was mainly at Matsushiro and Wakaho as was in the second period but it extended gradually to the eastern part of Koshoku and to the northern part of Sanada. Large shocks with intensity of IV or V on the JMA scale also occurred during this period. In November 1966, the frequency of earthqakes decreased greatly compared with the previous month and large shocks also did not take place. The fourth stage of activity: We call the period from January to the present the fourth stage of activity. The special feature of this stage was that the earthquakes that had clustered in the area of Matsushiro in the earlier stages of activity decreased in number remarkably, while the seismic area extended widely northeastward and southwestward, many shocks taking place in a part of Wakaho and in the southern part of Mt. Kamuriki. This paper will compile the result of our seismographic observation carried out during the period from December 1966 to February 1967 as the fourth report continuing from our previous ones. The seismographs used at each station were the HES 1-0.2 electromagnetic seismograph and the Ishimoto acceleration seismograph, of which the constants were indicated in Table 1 in our second report. The members of the Institute who participated in the field observation were: T. Hagiwara S. Saito, I. Karakama, M. Watanabe, T. Takahashi and Y. Ishikawa and the members of the Institute engaged in interpretation and analysis of seismograms being: T. Hagiwara, T. Iwata, K. Makino, N. Kamata, M. Kino, Y. Miura and R. Kawashima.
1965年8月3日に始まる長野県松代町地域の群発地震は, 1967年2月28日に至る19カ月を,4つの地震活動期に分けて考えることができよう.第1期の地震活動 発生より1965年11月に至る期間で,このときの主な有感地震の発生地域は皆神山の周辺,特にその南西部で,大きな地震はすべてこの地域に発生した.なお,第1期では若穂町保科週辺に極めて少数の有感地震が認められている.
URI: http://hdl.handle.net/2261/12362
ISSN: 00408972


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