seismic exploration using active sources at kuchi ...seismic exploration using active sources at...

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腍腊腜腚腘腋腐腇腂腃腉腔腎腗腓腖腏 腖腏腈腌腛腆腒腙腈腕腑腇腄腁腅腍腶膟膜 +*膄臐腬腴 +腧臐臆膆 ,膽腍膯膋 -膷膲 .腠臧膚臕 /膢臔臜腘 0膸臊 膐膋 1膫膦腭腸 2膠膝 3臃臔腱腝 +*腤膴腸膋 +*臉膔膍腼 ++腌腫 +腾膄膶 +臈膻臑膀膩 +Hetty Triastuty +膣腱臤腺 +膫膺腺腵 ,臡臔臁膡 ,膥膤臀腵 ,腍膭臘 -膸臊腡臓 -腓腱臚臉 .臗膖腮膉 /腣膤腵腺 /臉臠膑腎 /0臉膷腊 0腐膷 1腋膾 1腢膤 2腍膖腝臂 2膰膷腅腆腽 2臄膓 3膂膾膞 3臉臗膏腎臣 +*膖腜臙膫 +*腍腶腰臖 ++膱腕腷腺 +,腮臅 2+腦膹膫腚臍膁腯腥膒,臎腙膿膫腚膫腚腏臝腚腯腥腖-膎膷膫腚膇腲腹腚臇.膼臎膫腚膫腚腏臝腚 腯腥腖/膼腦腹腨膫腚腗膄臞膨腯腥腇腉腈腀0膼腦膫腚膮膛腯腥膒1臒腳腔膫腚膫腚腏臝腚腯腥 2腦膹膫腚膫腚腏臝腚腯腥腖3腩膌膫腚膫腚腏臝腚腯腥腏+*膊膈膺膫腚臝腚臇++腟膕膳臈腒腞 腪腟膕膪+,腟膕膳膊膈膺膮臌腟膕膪 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 Aoki 0, Toshiki Watanabe 1, Takahiro Ohkura 2, Hiroshi Shimizu 3, 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 Tsuji 0, Yasuhiro Hirata 0, Takashi Okuda 1, Taku Itoh 1, Shin Yoshikawa 2, Hiroyuki Inoue 2, Sayaka Ikeda 2, Mio Hori 3, Masaki Saito 3, Shuichiro Hirano +*, Yudai Uekama +*, Motoharu Iguchi ++, Takahiro Takeshita +,and Takehiko Mori 2+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, 0Earthquake Research Institute, University of Tokyo, 1Graduate School of Science, Nagoya University, 2Graduate School of Science, Kyoto University, 3Graduate 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] 腂腄23++.+3 膊膈膺膅膃膺腑膄膴 +1,,+3Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2* ,**/pp. ++.* 11

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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]  ¡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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Page 3: 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. +. 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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Fig. ,. Monthly number of volcanic earthquakes at Kuchierabujima volcano.

Fig. -. Underground structure at a shallow part be-

neath Shindake, revealed by geophysical observa-

tions.

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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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Arrow shows seismogram at the station closest to shot point in each record section.

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Page 7: 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. 0. Record sections of seismograms on NS line for (a) Shot S/, (b) Shot S+3, (c) Shot S+2, (d) Shot S0. Amplitude of

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

Arrow shows seismogram at the station closest to shot point in each record section.

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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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cde()* / km#�f��a�+ghij>kl>@� m/n�oO9p=�qr�,( ��()�,������ ij�s@t�+qr��u�()v>� P�m/+� / km�s,w'O�:* / km#�Ak9xy>�a�+�� �z�{@�|@}� ~9������6�[�U:* -�>� ����TU:a��Figs. 2� 3� +*�[U* Figs. /� 0,������m/ /

km�s> reduce( 9:* `���� + km���a�t�+���k��V�:�v�k�m/�_�6�� ,�:* S/� S2� S3� S+*� S+3E�>+�t�m/�+.- km�sC,.- km�s,�m>Q:* S+� S,� S.� S0� S++

>+� ,.0� ,.3� ,.2� -.*� ,.0 km�s, - km�s�k9* �������(9H��V�:�t�m/+ ,..C,./

km�s>�����S��)* bcde()���P��� 9:������������������V#WH��a����U:�� 9�����>Aa��z�{@+ *.,C*.- s,|@}� `�������� 9�#� P�m/����>Q:�,�#:A�,¡¢�:* ������H£k}>+¤¥����¦�§�|@9)Z� P�m/� ,./ km�s,( �¦��¨�©�)A�� Fig. ++�[U* ������m/ /

km�s> reduce( Q:* ª«� �� / km�>+ -.-

km�s¬/� / km<f>+ /.* km�s¬/>Q:�,�¢t:* -�>A������H��V�:a��z�{@+ *., s¬/��U:* H��¤¥� FACD¥jL,H£k}�¤¥� FECLL ��� bcde( Q:�� ª( H£k}�¤¥����a��­}� H�=� P�m/�m9���Q:�,�[�O�:*

0� � ����>�®¯°±>+� ²�_³� P�m/���U:�t�m/� 0 km�s�qr���}�xY� S�� 9: F�´z� µ��I� ,**-L* (t(E��¶·�°±>+¥j¸�$|>A +- km,¹9)Z�� ²�_³��(),¡¢�:_`��¤¥O�Et�)* /

km�s�m/>��()qr�+������H�p���U:v�u�()º»6�¦9*

Fig. 1. Travel times for all the shots.

K� ¨] I

¼ 18 ¼

Page 9: Seismic Exploration Using Active Sources at Kuchi ...Seismic Exploration Using Active Sources at Kuchi-erabujima Volcano, Southwest Japan Masato Iguchi+*, Keigo Yamamoto+, Takeshi

���� �+331� ������ ���� ���� S,��� ���� �������� !"#$%&�' . km ()*+, P#-.$ -.- km�s

/012�&34 5 6 78 �9:��;&��"<=1 >.*+ ,.*?,., km�s -.@ABCD3/2�&34 EF G�C"HIJ , km?. km�K&��-.- km�sLM N*O-.@PQ��KR6 STUV WX@Y+� 4 S+1Z S+2[\�9:� ����3!"# N*O-.� ,..?,./ km�sCDR6 78Z]8 ^_�R` 72&�a -.� ,.. km�sb./01��34c���� �+ kmd�� N*O-.$ef2 W

X6 N*O-.�6 c���� gh !i/jk2�&3l/@Q*� 4 Table 0�c���� N*O-./mn !i$5/o�p2 4 S/6 S26 S36 S+*6S+3[\qrs��9*+t u�C�N*O-.@+.- km�s?,.- km�s/v-CD34 l��6 qrs�*+wx�� s�y@z{|}2�&3~���B�34 ��6 ��y@g_5CPQ��&3~�C�N*

O-.@�-/[��&34 ���6 ����y` S

06 �����y ` S++6 78��y S,C�6 -.*6,.06 ,.3 km�s��2�&34 ]&�� ��yC�UVC6 �����y�D3 S+C� ,.0 km�s, 5 6 ���s� ��y����3 S.C� ,.2 km�s/[��&34 5 6 gh@���KKQ��&��!i����qrs� ��y@�{� @��&3¡����3S1K�¢ S+0C�N*O-.@�-CD34£�6��y ¡¤¥/���&3!¥C�N*O-.@v-[~¦�D34 S+./ S+/�&§��78��y ¨©�D3@6t�ª� +.3 km�sK�¢ ,., km�s/v-CD34S+. ~¦6 mn����y |}«@|}2�&3478��y� -¬ ��y*+[3/���KR �­®6 +303�6 S+/�t ¯° +¬ ��y ±²���26 ��y±² ³´@|}2�&3 o�v-/[��&3µ¶·@D34

1� � �,**.¸ ++¹����s��K&�º»!"��

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.

���s��KO3º»!"G�

¼ 19 ¼

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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������1�� ,**. �����e3���2 +****�G� e�m��� 3 A�4�i#1�#( ,**.

��g�(!�� V*//-P*-0.

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, --/�-.-.

t�4|��3�� ,**, �����e3�=J�����!] �56��e3������e3�����*! +-1�+.,.

t�4|�3�����3�7������M���������y����,���8 ,**, �����e3�=Je3�Af�*� zk�#�=jk��. ..B-+ -+1�-,0.

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:;�A��c£����!�� +301 ¤? .+� ++   ,,��������"�H^ @¡¢£�c£A. ,, 13�32.

¤(¥u +31* ������e3�m��m�*¦� +303��Af*! :;�K�Af�e3�m ¤? ./� -   ,.�-+.

§( ¥��t¦. ,**- §¨©Bª«¨¬@��e3�¨��m­ �©® zk�#�=jk��. .0B 131�2*-.

zk�#�=jk� +32* �����e3�=JAf*! e3 e!X�B((. +3 .,�.0.

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zk�#�=jk���zYT�#Y#��:;��#�#� +32+ +32*� %3   ,2�& �������"� e%°.& e3 e!X�B((. ,* +�3.

z�C� +3-. ������AD�«/� e3� +� , ,*�-3.

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

°(���G��± +330 e3Z[\����³��²³�´µ@¬Z[@�y^ e3 .+ +,1�+-3.

�'6(�¢ ,**- ´3�=J|YAf���*!=�wlm�µ®¶+� Afjk�>. 12 +,+�+.-.

(�3{· +3-/ ������" e�e��¶¸·w¸¬G�3¹º e3� +� , --3�-/..

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

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

3����t�4|��3I7���?� +331 +330������e3�Af�m��^¯�]/� zk�#�=jk��. .*B-+ -3�.1.

»��·�¬­D��M ¼ +302 ������A�3�#®N� zk�#�=jk��. ++A +--�+.*.

%Received March -, ,**/&%Accepted August +0, ,**/&

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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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Table +�,. (continued)

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Table +�-. (continued)

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Table +�.. (continued)

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

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Table -�,. (continued)

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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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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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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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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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Table /�-. (continued)

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Table /�.. (continued)

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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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