Three-Dimensional P and S Wave Velocity Structure in the Focal Region of the 1984 Western Nagano Prefecture Earthquake

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

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The detailed three-dimensional P and S wave velocity structure in the focal region of the 1984 Western Nagano Prefecture Earthquake occurring close to an active volcano, Mt. Ontake, central Japan, is derived from a tomographic inversion of travel time data obtained by the 1986 Joint Seismological Research in Western Nagano Prefecture. The data set includes 7,693 P-wave and 6,070 S-wave arrival times observed at 49 stations from 212 local earthquakes and 2 explosions. The velocities in the shallow portion of upper crust are determined at each grid point with its spacing of 1-2 km and good resolutions are obtained from the Earth's surface to a depth of 4 km. There exist strong lateral heterogeneities especially from the surface to a depth of 1 km. The seismic velocity map obtained in the height of 1 km above sea level well corresponds to the maps of surface geology and Bouguer gravity anomaly. This correspondence, however, is not so clear in the deeper layers. And, the greater the depth, the less heterogeneous the velocity structure. The velocity distribution on the fault seems to correspond to the distribution of dislocation and rupture front estimated from an analysis of strong motion and geodetic data: the low velocity region has the large amount of dislocation and the retarded rupture front.

Original languageEnglish
Pages (from-to)343-360
Number of pages18
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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    Wada, H., Takeuchi, F., Mikumo, T., Kurata, Y., Kuriyama, S., Koizumi, M., Hirahara, K., Hirano, N., Kaneshima, S., Nakamura, T., Nishigami, K., Oike, K., Shibutani, T., Okura, T., Hirata, N., Kanazawa, T., Tomita, S., Yabuki, T., Ooida, T., ... Yokohama, M. (1992). Three-Dimensional P and S Wave Velocity Structure in the Focal Region of the 1984 Western Nagano Prefecture Earthquake. journal of physics of the earth, 40(2), 343-360. https://doi.org/10.4294/jpe1952.40.343