Focal Mechanism Analyses of Aftershocks of the 1984 Western Nagano Prefecture Earthquake
| Autor: | Manabu Yokohama, Takuo Shibutani, Toru Matsuzawa, Mamoru Yamada, Akio Takagi, Satoshi Kaneshima, Sadaomi Suzuki, Akihiko Yamamoto, Shoji Tomita, Megumi Mizoue, Makoto Koizumi, Toru Ouchi, Rikio Miyajima, Kaname Sakai, Tetsuichiro Yabuki, Kazuro Hirahara, Masahiro Kosuga, Iwao Fujii, Yasuhiro Umeda, Ikuo Karakama, Katsumi Miura, Takuo Okamoto, Masayuki Suzuki, Toshihiko Kanazawa, Toshio Haneda, Toshio Mitsunami, Kin'ya Nishigami, Akio Kuroiso, Takeo Moriya, Yuji Kurata, Shin'ichi Hashimoto, Masayoshi Takahashi, Toshikazu Tanada, Takahiro Okuda, Hiroo Wada, Kiyoshi Ito, Harumi Aoki, Tooru Ooida, Akira Hasegawa, Toshio Kono, Akira Ikami, Tameshige Tsukuda, Hiroki Miyamachi, Fumihito Yamazaki, Ken'ichiro Yamashina, Kazuaki Miura, Norio Hirano, Akihiko Ito, Tatsuo Saeki, Kazuo Oike, Masaru Nakamura, Yoshihisa Iio, Atsushi Nakajima, Satoru Kuriyama, Toru Nakayama, Fumiaki Takeuchi, Isao Nakamura, Masaru Kobayashi, Takeshi Mikumo, Yukio Ishiketa, Naoshi Hirata, Shigeki Horiuchi |
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| Rok vydání: | 1992 |
| Předmět: | |
| Zdroj: | Journal of Physics of the Earth. 40:327-341 |
| ISSN: | 1884-2305 0022-3743 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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