Hypocenter Locations by a Dense Network

Akio Takagi, Toshio Kono, Toru Nakayama, Akira Hasegawa, Toru Matsuzawa, Shigeki Horiuchi, Shigeki Horiuchi, Akio Kuroiso, Kiyoshi Ito, Yasuhiro Umeda, Kazuo Oike, Yoshihisa Iio, Kinya Nishigami, Kiyoshi Ito, Kinya Nishigami, Sadaomi Suzuki, Takeo Moriya, Akihiko Yamamoto, Masaru Nakamura, Mamoru YamadaTooru Ooida, Rikio Miyajima, Fumihito Yamazaki, Harumi Aoki, Iwao Fujii, Akira Ikami, Akira Ikami, Toru Ouchi, Toshikazu Tanada, Manabu Yokohama, Tameshige Tsukuda, Toshio Haneda, Shin Ich Hashimoto, Ken Ichiro Yamashina, Katsumi Miura, Yukio Ishiketa, Isao Nakamura, Megumi Mizoue, Masaru Kobayashi, Masayoshi Takahashi, Kaname Sakai, Takahiro Ohkura, Tatsuo Saeki, Fumiaki Takeuchi, Hiroo Wada, Takuo Shibutani, Kazurou Hirahara, Satoshi Kaneshima, Makoto Koizumi, Yuji Kurata, Satoru Kuriyama, Takeshi Mikumo, Norio Hirano, Naoshi Hirata, Toshihiko Kanazawa, Tetsuichiro Yabuki, Shoji Tomita, Akihiko Ito, Masayuki Suzuki, Masahiro Kosuga, Atsushi Nakajima, Kazuaki Miura, Toshio Mitsunami, Takuo Okamoto

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A dense temporary seismograph network was set up in the aftershock area of the 1984 Western Nagano Prefecture Earthquake of M 6.8 by the group for the 1986 Joint Seismologieal Research in Western Nagano Prefecture. Seismograms of about 1,500 events were obtained during the observation period of 52 days from September 1 to October 22, 1986, and 530 events in and around the aftershock area were located precisely. Extent of the aftershock area is about 20 km in the east-west and about 7 km in the north-south. The hypocenter distribution in the present study shows that the depths of the deepest aftershocks become deep toward the west. The maximum depth in the eastern part of the aftershock area is about 6 km and it becomes 10 km at the western end. Seismic activity is high at a belt near the maximum depths of the aftershock area and no events were detected below this seismic belt. It was also found that the size and location of the aftershock area found by the present observation are almost the same as that obtained by a temporary seismic observation in 1984, which was made just after the main shock. Since no events below the inclined lower boundary were found in either of the observations, it is suggested that the deeper region below the boundary cannot accumulate stresses sufficient to generate earthquakes, suggesting the existence of large locality in the lower boundary of seismogenic zone.

Original languageEnglish
Pages (from-to)313-326
Number of pages14
Journaljournal of physics of the earth
Volume40
Issue number2
DOIs
Publication statusPublished - 1992 Jan 1

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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    Takagi, A., Kono, T., Nakayama, T., Hasegawa, A., Matsuzawa, T., Horiuchi, S., Horiuchi, S., Kuroiso, A., Ito, K., Umeda, Y., Oike, K., Iio, Y., Nishigami, K., Ito, K., Nishigami, K., Suzuki, S., Moriya, T., Yamamoto, A., Nakamura, M., ... Okamoto, T. (1992). Hypocenter Locations by a Dense Network. journal of physics of the earth, 40(2), 313-326. https://doi.org/10.4294/jpe1952.40.313