Focal Mechanism Analyses of Aftershocks of the 1984 Western Nagano Prefecture Earthquake
Focal Mechanism Analyses of Aftershocks of the 1984 Western Nagano Prefecture Earthquake
复制标题
1984年长野县西部地震余震震源机制分析
DOI：
10.4294/jpe1952.40.327
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
M. Yokohama
中科院分区：
文献类型：
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作者：
F. Yamazaki;S. Horiuchi;K. Ito;T. Moriya;K. Nishigami;Tooru Ooida;T. Ouchi;T. Tanada;T. Tsukuda;H. Aoki;Iwao Fujii;T. Haneda;A. Hasegawa;S. Hashimoto;K. Hirahara;Norio Hirano;N. Hirata;Y. Iio;A. Ikami;Yukio Ishiketa;A. Ito;T. Kanazawa;S. Kaneshima;I. Karakama;M. Kobayashi;M. Koizumi;T. Kono;M. Kosuga;Yuji Kurata;Satoru Kuriyama;A. Kuroiso;T. Matsuzawa;T. Mikumo;Toshio Mitsunami;K. Miura;K. Miura;R. Miyajima;H. Miyamachi;M. Mizoue;Atsushi Nakajima;Isao Nakamura;Masaru Nakamura;T. Nakayama;K. Oike;T. Okamoto;T. Okuda;T. Saeki;K. Sakai;T. Shibutani;Masayuki Suzuki;Sadaomi Suzuki;Masayoshi Takahashi;A. Takagi;F. Takeuchi;Shoji Tomita;Y. Umeda;H. Wada;T. Yabuki;M. Yamada;A. Yamamoto;K. Yamashina;M. Yokohama
利用1986年长野县西部联合地震研究（JSR'86）地震观测项目获得的数据集，对日本中部Ontake火山附近的震源机制进行了研究。数据集主要包括1984年长野县西部地震（M=6.8）余震的p波初动。共选取556个事件进行震源机制分析。此外，还利用了周边大学常规网络的纵波数据。成功分析了四百个事件。根据震源机制的类型和事件的空间分布，我们将这些事件分为以下4类：(1)1984年主震断裂带的走滑型事件，其共同节面与ENE-WSW走向节面平行；(2)在主震东北方向已存在地震群的区域出现逆断层型事件，可能与主震引发的地震群有关；(3)发生在最大余震（M=6.2）附近的逆断层型事件，但不是最大余震的连续余震序列；(4)在JSR'86运行前未观测到的最东端深度的走滑断层类型事件。所获得的多种震源机制和震源的空间分布表明，御武火山周围是一个由至少2种裂缝组成的复杂地震构造。
Focal mechanisms around Ontake Volcano, central Japan, were investigated by using the data set obtained by a seismic observation project of the 1986 Joint Seismological Research in Western Nagano Prefecture (JSR'86). The data set included P-wave first motions of aftershocks of the 1984 Western Nagano Prefecture Earthquake (M=6.8) mainly. A total of 556 events was selected for the focal mechanism analysis. The P-wave data from the surrounding university routine networks were also utilized additionally. Four hundred two events were successfully analyzed. Based on the types of focal mechanisms and on the spatial distribution of the events, we classify these events into the following 4 groups: (1) events of strike-slip fault type with a common nodal plane parallel to the ENE-WSW striking nodal plane in the fracture zone of the 1984 main shock; (2) events of reverse fault type in the area of the preexisting earthquake swarm to the northeast of the main shock, in a possible relation with an earthquake swarm activated by the main shock; (3) events of reverse fault type that occurred near the largest aftershock (M=6.2), but are not the continued aftershock sequence of the largest aftershock; (4) events of strike-slip fault type at depths to the easternmost part where no activity had been observed before the operation of JSR'86. The plural types of focal mechanisms obtained and the spatial distribution of foci suggest a complex seismo-tectonic structure that consists of at least 2 kinds of fracturings around Ontake Volcano.