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Univ. Tokyo
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Seismic exploration at Fuji volcano with active sources
The outline of the experiment and the arrival time data
Jun Oikawa+, Tsuneomi Kagiyama+a, Satoru Tanaka,b, Hiroki Miyamachi-, Tomoki
Tsutsui., Yasushi Ikeda/, Hiroaki Katayama/, Norimichi Matsuo0, Hiromitsu Oshima1,
Yuichi Nishimura1, Keigo Yamamoto2, Toshiki Watanabe3, Fumihito Yamazaki3, Hidefumi Watanabe+, Toshitsugu Fujii+, Setsuya Nakada+, Minoru Takeo+, Takao Ohminato+, Takayuki Kaneko+, Mitsuhiro Yoshimoto+c, Toyotarou Takeda+d, Etsurou
Koyama+, Noboru Osada+, Mamoru Saka+, Toshio Haneda+, Shinichi Hashimoto+, Hiroshi Tsuji+, Yoshiko Imoto+, Taketo Shimano+e, Akiko Furukawa+, Takeshi Sagiya3,
Iwao Fujii3f, Yoshinari Hayashi3, Rikio Miyajima3, Mamoru Yamada3, Takashi Okuda3,
Takeo Itoh3, Takeshi Hashimoto1, Tokumitsu Maekawa1, Atsuo Suzuki1, Taku Itoh1g,
Yasushi Miura1, Sadato Ueki,, Takeshi Nishimura,, Kouichi Nita,d, Mineji Satoh,h,
Youichi Simomura,, Kenji Nogami+*, Sin’ya Onizawa+*i, Hiroko Oyamada++j, Jun
Funasaki/, Shin Chikazawa/, Kenji Fujiwara/, Nobuo Hamada/, Gen Aoki/, Akimichi
Takagi/, Tetsuya Yamamoto/, Yutaka Hayashi/, Masaki Kanao+,, Mikiya Yamashita+,b,
Hiroshi Shimizu0, Atsushi Watanabe0, Masahiro Korenaga0k, Takahiro Ohkura+-, Shin
Yoshikawa+-, Sayaka Ikeda+-l, Masato Iguchi2, Takeshi Tameguri2, Hiroshi Yakiwara-,
Shuichirou Hirano-
Earthquake Research Institute,University of Tokyo, , Graduate School of Science,Tohoku University, - Faculty of Science,Kagoshima University, . Faculty of Engineering and Resource Science,
Akita University, / Japan Meteorological Agency, 0 Graduate School of Sciences, Kyushu University, 1 Graduate School of Science, Hokkaido University, 2 Disaster Prevention Research Institute,
+
* e-mail : [email protected] ©º++-ῌ**-, |}’}»+M +ῌ+ῌ+
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Kyoto University, 3 Graduate School of Environmental Studies, Nagoya University, +* Volcano
Fluid Research Center, Tokyo Institute of Technology, ++ Faculty of Science, Chiba University,
+,
National Institute of Polar Research, +- Graduate School of Science, Kyoto University, a Now at
Graduate School of Science,Kyoto University, b Now at Japan Agency for Marine-Earth Science and
Technology, c Now at Graduate School of Sciences, Hokkaido University, d Now retired, e Now at
Colledge of Environment and Disaster Research, Fuji Tokoha University, f Tono Research Institute
of Earthquake Science, g Now at JALWAVE COMPANY, LTD., h Now at Hakusan Corporation, i Now
at National Institute of Advanced Industrial Science and Technology, j Now at Earthquake Research
Institute, University of Tokyo, k Now at Railway Technical Research Institute, l Now at Japan
Meteorological Agency
Abstract
Fuji volcano (altitude -,110m) is the largest basaltic stratovolcano in Japan. In late August and
early September ,**-, seismic exploration was conducted around Fuji volcano by the detonation of
/** kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an
eigenfrequency of , Hz were used for observation, positioned along a WSW-ENE line passing
through the summit of the mountain. A total of .03 seismic stations were installed at intervals of
,/*ῌ/** m. The data were stored in memory on-site using data loggers. The sampling interval was
. ms. Charges were detonated at / points, one at each end of the observation line and - along its
length. The first arrival times and the later-phase arrival times at each station for each detonation
were recorded as data. P-wave velocities in the surface layer were estimated from the travel time
curves near the explosion points, with results of ,./ km/s obtained for the vicinity of Fuji volcano
and ..* km/s elsewhere.
Key words : Fuji volcano, seismic exploration, seismic velocity structure of volcano, National Project for Prediction of Volcanic Eruption
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Fig. +. Tectonic setting around Fuji volcano, Japan and location map of the seismic exploration. EUR, NAM, PAC and
PHS stand for Eurasian, North American, Pacific and Philippine Sea plates, respectively. Solid triangles show active
volcanoes and open triangle indicates Fuji volcano. Stars and open circles indicate shot points and observation
points, respectively.
Table +. Shot times, locations of / explosions in the experiment.
The coordinates are presented by WGS2..
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Locations of observation points. The coordinates are presented by WGS2..
79 ῍῏ ῎ ῐ
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81 ῍῏ ῎ ῐ
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Table ,.
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Table -. Arrival times (arrival(s)), polarity (P) and quality rank of the first motion (R) at each station for all
shots. Ranks A, B, C indicate that accuracies of the first arrival times are within +* ms, -* ms, +** ms,
respectively, and polarities are determined. Rank D indicates that accuracy is within +** ms and polarity
is undetermined. Rank L indicates that accuracy is more than +** ms and polarity is undetermined.
Rank X indicates that no first motion is identified. Polarities of U and D indicate that directions of the
first motion are upward and downward, respectively. Polarity of X means undetermined one.
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91 ῍῏ ῎ ῐ
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ῌ 92 ῌ
Table -.
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93 ῍῏ ῎ ῐ
Table ..
Arrival times of the later phase for shot S,.
ῌ 94 ῌ
Table /.
Arrival times of the later phase for shot S..