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Page 1: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

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Seismic Exploration Using Active Sources at Kuchi-

erabujima Volcano, Southwest Japan

Masato Iguchi+�*, Keigo Yamamoto+�, Takeshi Hashimoto,�, Tomoki Tsutsui-�, Satoru

Tanaka.�, Shin’ya Onizawa/�, Yosuke Aoki0�, Toshiki Watanabe1�, Takahiro Ohkura2�,

Hiroshi Shimizu3�, Hiroshi Yakiwara+*�, Hiroki Miyamachi+*�, Hideyuki Hiramatsu++�, Take-

shi Tameguri+�, Tetsuro Takayama+�, Masayo Fukushima+�, Hetty Triastuty+�, Kazuhiro

Ishihara+�, Hiromitsu Oshima,�, Atsuo Suzuki,�, Tokumitsu Maekawa,�, Tatsuya Kajii-�,

Yoshiaki Watanabe-�, Yohei Ogiwara.�, Kenji Nogami/�, Mitsuhiro Oikawa/�, Jun-ichi

Hirabayashi/�, Hiroshi Tsuji0�, Yasuhiro Hirata0�, Takashi Okuda1�, Taku Itoh1�, Shin

Yoshikawa2�, Hiroyuki Inoue2�, Sayaka Ikeda2�, Mio Hori3�, Masaki Saito3�, Shuichiro

Hirano+*�, Yudai Uekama+*�, Motoharu Iguchi++�, Takahiro Takeshita+,� and Takehiko

Mori2�

+�Disaster Prevention Research Institute, Kyoto University, ,�Graduate School of Science, Hokkaido

University, -�Faculty of Engineering and Resource Science, Akita University, .�Graduate School of

Science, Tohoku University, /�Volcanic Fluid Research Center, Tokyo Institute of Technology,0�Earthquake Research Institute, University of Tokyo, 1�Graduate School of Science, Nagoya

University, 2�Graduate School of Science, Kyoto University, 3�Graduate School of Science, Kyushu

University, +*�Faculty of Science, Kagoshima University, ++�Fukuoka District Meteorological Obser-

vatory, +,�Kagoshima Local Meteorological Observatory

Abstract

Seismic exploration using artificial sources was conducted at Kuchierabujima volcano, south-

west Japan in November ,**. by .* participants from 3 national universities and Japan Meteoro-

logical Agency to investigate the subsurface seismic structure. The exploration was the ++th joint

experiment under the National Project for Prediction of Volcanic Eruptions. A total of +2- temporal

stations equipped with a ,Hz vertical component seismometer (including 1/ --component seismome-

ters) and a portable data logger were deployed on Kuchierabu Island. Dynamite shots with charges

of +*�++/kg were detonated at +3 locations, and seismic signals were successfully recorded. To

* e-mail : [email protected]  Â¡23+�+.+3 ��<¢£<¤�) +1,,�+3�

� � x y z ¥ ¦Bull. Earthq. Res. Inst.

Univ. TokyoVol. 2*  ,**/� pp. ++�.*

§ 11 §

Page 2: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

reveal the P-wave velocity structure, ,3// arrival times of the first motion were picked from the

seismograms, and ,+21 were classified into ranks A and B. From the record sections and the arrival

time data, characteristics reflecting the geological structure were identified. Refracted waves of /

km/s were observed at stations�/km from the shot points. Apparent velocities near the shot

points depend on the surface geology around the shots. P-wave arrived earlier at stations near the

summits. Strongly scattered waves were observed similarly near the summits.

Key words : Kuchierabujima volcano, seismic exploration, seismic velocity structure, National Pro-

ject for Volcanic Eruption

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Fig. +. Geological map of Kuchierabujima volcano (Geshi and Kobayashi, ,**.). Index map is shown at the left side.

S : Shindake, F : Furudake, N : Noike. Under ground structure of Shindake along the dashed line is shown in Fig. -.

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Page 4: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

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Page 6: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

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each trace is normalized by the maximum value. The reduction velocity is /.*km/s. Lapse time is from shot time.

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Page 8: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

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Fig. 2. Plots of travel times for (a) Shot S+, (b) Shot S,, (c) Shot S-, (d) Shot S., (e) Shot S/, (f) Shot S0. The

reduction velocity is /.* km/s.

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Page 10: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

�������� �� ������������� +2-������� +3 !�"#��$%&'(����)�* 0-��+,� -�./0�123�4 5�67 1�)89:;< P)=>?�@�A

BCD��� )89:EF@;<��� ���$G��H���IJKLM3NO<� PQRST�U%&�V�WXY�Z[�

Fig. 3. Plots of travel times for the shots at the flank of Kuchierabujima. (a) Shot S1, (b) Shot S2, (c) Shot

S3, (d) Shot S+*, (e) Shot S++, (f) Shot S+,, (g) Shot S+-, (h) Shot S+., (i) Shot S+/ and (j) Shot S+0. The

reduction velocity is /.*km/s.

\� ]^ _

` 20 `

Page 11: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Fig. +*. Plots of travel times for the shots at the summit of Kuchierabujima. (a) Shot S+1, Shindake, (b) Shot

S+2, Furudake and (c) Shot S+3, Noike. The reduction velocity is /.*km/s.

Fig. ++. Plots of travel times for (a) Shot S+, (b) Shot S,, (c) Shot S-, (d) Shot S., (e) Shot S/, (f) Shot S0.

Open and solid circles indicate travel times of stations at the flank (Line A-D) and near the summits (Line

E-L), respectively. The reduction velocity is /.* km/s. Elevation correction is made on travel times.

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Page 12: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

� ��������������������������� ���������������� ���������� ��������� ����!"��#$ %&��� ����'�(� %&���� �) ��*!��"�#�+$,��-.%��/�0����� �� &'�1����� �2�3 �&4��5 �&�( �&,6789:� �&;��<�����=)���+����*� >+,-��.����/��?@ABCD0�E81FG�2+=)���+���� �� 3�45�6�������1��57.5H�I�+ =89.=EJ�����:;�K<��=L ����� ���M>?�

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Iguchi, M., +33+, Geophysical data collection using an inter-

active personal computer system (part +) �Experimen-

tal monitoring at Suwanosejima volcano�, Bull. Vol-

canol. Soc. Japan, -0, --/�-.-.

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9u���t�4|�¬­D��Solihin, A., ,**, ������"�E±F�²A¨�#®�_¯] �56��e3������e3�����*! +/3�+02.

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ptqr�¢ +330 |YAf����=�e3��Afº»³[\��¹�+%���n� e3 .+ ,,1�,.+.

º¹�¼�(��?�§( ¥ ,**, �����e3�=J��¨�!H �56��e3������e3�����*! +,+�+,1.

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Page 13: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table +�+. Locations of seismic stations. The coordinates are based on WGS2..

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Page 14: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table +�,. (continued)

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Page 15: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table +�-. (continued)

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Table +�.. (continued)

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� 26 �

Page 17: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table ,. Shot locations, times and charge sizes for +3 explosions in the experiment.

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Page 18: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table -�+. Arrival times and polarities of the first motions for shots S+ to S0.

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Page 19: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table -�,. (continued)

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� 29 �

Page 20: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table -�-. (continued)

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Page 21: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table -�.. (continued)

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� 31 �

Page 22: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table .�+. Arrival times and polarities of the first motions for shots S1 to S+,.

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Page 23: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table .�,. (continued)

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� 33 �

Page 24: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table .�-. (continued)

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� 34 �

Page 25: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table .�.. (continued)

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Page 26: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table /�+. Arrival times and polarities of the first motions for shots S+- to S+3.

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Page 27: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table /�,. (continued)

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Page 28: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table /�-. (continued)

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Page 29: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table /�.. (continued)

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� 39 �

Page 30: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

Table 0. Apparent P-wave velocities near the shot points.

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