24
腘腎腍腃腁腂腉腒腋腖腑腕腌 腊腔腁腇腅腓腏腄腗腆腐腈腮臓 +膀膝膎臄 +a 臭臥 ,b 腯臧膊膭 -至腑臢膭 .臣臭 /腢膝膍/0臝臰膍膈 1臏臚1腻膆 2膴膭 3膝膚3+致腑+臥臭臑+腆腂 +腑腢腛 +腷膢+膲膊 +c 臤臭+d 膹膝腗 +臨臭 ++腔臭腃腄 +臀腒 ++腐腣+臘臟腈腛 +腡臆 +e 膅臓膏膢 +膛臟 3致腑 3f 臻臊 3腯臰3膝臭 3腘臭 3腎致腆腛 3腐腆1臔臓臶膈 1腦腕臸臎 1腎致 1g 膜腕 1自臆 ,臏臚臛膤 ,臇臭膇膣 ,d 膖致,h 腚臚,膽腽膧 +*+*i 膹膝臭膑膢 ++j 膱膚 //致膂腽膧 /臭臀臎 //腕腧///臋腪 +,膝腚腥+,b 臍臈 0臷膤 0臉腖膸膊 0k 臝臕腼膊 +-腭臓 +-臣臭腅腆膒 +-l 腑膉臌臆 2腐腺 2腀腕-腉腗膱腒-+臲腱臝腠臡臅腾腰膷,臝腠臝腠腓腠腾腰腛-膨膦臰臝腠.膰臭臝腠膋腠膥膃腠/腩膼臦0腸膮臝腠臝腠腓腠腾腰腓1腞臵臝腠臝腠腓腠腓2腱臯臝腠膗腾腰膷3膅腙臝 腠臝腠腓腦腲腠腾腰腛+*臲腱膋腴臝腠腜膝臜腾腰腊腍腋腀++臝腠+,腵臡腾腰膷 +-腱臯臝腠臝腠腓腠腾腰腛a 膄腱臯臝腠臝腠腓腠腾腰腛b 膄腞腾腰腟腨膐c 腞臵臝腠 臝腠腓腠腾腰腛d 膷臙e 膡膾臝腠腦腲膗腠f 膄臲臺臡臅腛腠腾腰膷g JAL 腈腉腇腌h 膄臼膝膋腴腣膩腝膫i 膄膞腴腬膳臖膔腾腰膷j 膄臲腱臝腠臡臅腾腰膷k 臬臵臖膔 腬膳腾腰膷l 膄腩膼臦 Seismic exploration at Fuji volcano with active sources The outline of the experiment and the arrival time dataJun Oikawa +, Tsuneomi Kagiyama +a , Satoru Tanaka ,b , Hiroki Miyamachi -, Tomoki Tsutsui ., Yasushi Ikeda /, Hiroaki Katayama /, Norimichi Matsuo 0, Hiromitsu Oshima 1, Yuichi Nishimura 1, Keigo Yamamoto 2, Toshiki Watanabe 3, Fumihito Yamazaki 3, Hide- fumi Watanabe +, Toshitsugu Fujii +, Setsuya Nakada +, Minoru Takeo +, Takao Oh- minato +, Takayuki Kaneko +, Mitsuhiro Yoshimoto +c , Toyotarou Takeda +d , Etsurou Koyama +, Noboru Osada +, Mamoru Saka +, Toshio Haneda +, Shinichi Hashimoto +, Hi- roshi Tsuji +, Yoshiko Imoto +, Taketo Shimano +e , Akiko Furukawa +, Takeshi Sagiya 3, Iwao Fujii 3f , Yoshinari Hayashi 3, Rikio Miyajima 3, Mamoru Yamada 3, Takashi Okuda 3, Takeo Itoh 3, Takeshi Hashimoto 1, Tokumitsu Maekawa 1, Atsuo Suzuki 1, Taku Itoh 1g , Yasushi Miura 1, 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 Shimizu 0, Atsushi Watanabe 0, Masahiro Korenaga 0k , Takahiro Ohkura +-, Shin Yoshikawa +-, Sayaka Ikeda +-l , Masato Iguchi 2, Takeshi Tameguri 2, Hiroshi Yakiwara -, Shuichirou Hirano -+Earthquake Research Institute,University of Tokyo, ,Graduate School of Science,Tohoku Univer- sity, -Faculty of Science,Kagoshima University, .Faculty of Engineering and Resource Science, Akita University, /Japan Meteorological Agency, 0Graduate School of Sciences, Kyushu Univer- sity, 1Graduate School of Science, Hokkaido University, 2Disaster Prevention Research Institute, * e-mail : [email protected] 腂腄++-**-, 臲腱臯腱腹+++Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2+ ,**1pp. 1+3. 71

Seismic exploration at Fuji volcano with active sources · Koyama+, Noboru Osada+, Mamoru Saka+, Toshio Haneda+, ... Yoshinari Hayashi3, Rikio Miyajima3, Mamoru Yamada3, Takashi Okuda3,

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+�|}�~������,�| �~�~�!~����-�����~!~"�.���~�~��~"�/�����0����~�~�!~����1� ���~�~�!~��2�}��~#�����3�$?��~�~���~����+*�|}���~��%��������++��&�~!~"�+,��' �����+-�}��~�~�!~����a¡}��~�~�!~����b¡����¢(£¤�c¡ ���~�~�!~����d¡)�¥�e¡*¦§&�~��#�~"�f¡|¨���~����g¡ ©ª�JAL

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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�, Hide-

fumi Watanabe+�, Toshitsugu Fujii+�, Setsuya Nakada+�, Minoru Takeo+�, Takao Oh-

minato+�, Takayuki Kaneko+�, Mitsuhiro Yoshimoto+�c, Toyotarou Takeda+�d, Etsurou

Koyama+�, Noboru Osada+�, Mamoru Saka+�, Toshio Haneda+�, Shinichi Hashimoto+�, Hi-

roshi Tsuji+�, Yoshiko Imoto+�, Taketo Shimano+�e, Akiko Furukawa+�, Takeshi Sagiya3�,

Iwao Fujii3�f, Yoshinari Hayashi3�, Rikio Miyajima3�, Mamoru Yamada3�, Takashi Okuda3�,

Takeo Itoh3�, Takeshi Hashimoto1�, Tokumitsu Maekawa1�, Atsuo Suzuki1�, Taku Itoh1�g,

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 Korenaga0�k, 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 Univer-

sity, -�Faculty of Science,Kagoshima University, .�Faculty of Engineering and Resource Science,

Akita University, /�Japan Meteorological Agency, 0�Graduate School of Sciences, Kyushu Univer-

sity, 1�Graduate School of Science, Hokkaido University, 2�Disaster Prevention Research Institute,

* e-mail : [email protected] ©º++-�**-, |}��}»+M +�+�+�

� � � � � , -Bull. Earthq. Res. Inst.

Univ. Tokyo

Vol. 2+ ©,**1� pp. 1+�3.

¼ 71 ¼

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

,/*�/** 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 Pro-

ject for Prediction of Volcanic Eruption

+� � � � ������ ������� �������������� ��� -,110 m�� ������ .** km-

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G:� +*H����IJ167�=� +1*1��K����L� -**M���IJ167N7������ ���������O�<6�P7=� !�QR�� ���=S������T�#$UVEW�P7J;��� X�Y� ,**+�� *2� ������Z[�\��N]�^_`��a������67�=� ����!����=������6�+� !���bP4c6�17����� X d� +31+�� ����ef_ghijklm=�!jklm;nlo^pjklm�"qrs�7�tu��+� v$�w#$%=�x�y&167�'z��� XFig. +� X�{� +323��

J� |����G(�'}� W�hm~����)��� J�*�N��m������=����*�N�������167�;��$567�� J� |N��������� O!�G(�'����+$#� �J;�� ���������,� �W�P4c6�-���� ���� ,**- 2�.#$ 3��c�#<6� � 0�����/0�����76��v52���G(��<���'�1�� -;� 2$52'�3-¡4� 56�;¢£��¤�� ��¥9N]���¦l§�¨ � J5$�¦l§#$2$5�©ª�� 7�8« �/9��� X:�¬� �­�S� ,**.a ; �­�S� ,**.b ; �­�S� ,**.c ; ;Y�S� ,**0��

,� ����� �®H���'�1��<��� +� ��������@�@�¯= �°v +* km>?*�� ,�±²?���³9� ,� ���@��'}���´Az#$�Bµ3� ¶C3�·�;!5$��D�¸9 �J;���� J�<E�¹� �2c�� Fig. +�º XS+� S,�S-� S.� K+� �¨ /'��56���12� 56��

�­ » S

¼ 72 ¼

���� DGPS���� GPS��� ������� ���������� + m�� ������� !"� /* m#�$%�&�'(��&)*+���� ,-.�� /0 +** mm12� 34 2* m�56� 70 ++..- mm, 84 ../ mm�9:�.;<�=)$>?4@ABC� D���,E� /** kg�F;!-�,E��G,-.;H<�IJ�K��LMNO,-4@��P@Q@�,-R�ST� U�� V�� ��� ,-MN� Table +OWXY6�5C� ,-OZ[C,-.�\]^_`,-ab�� c��defghijklm��n���� o�pqr , Hz, st(uvw ,., kx��

yz {Mark Productsh| L-,,D} ~�>�>?Lr*.1��B� S+^_` K+~������� 21 kmO^_���2O���� n�R� .03R�� �RO2���yz~� P��� 0+RO�����^_`����O�k�����yz~���A -��n�R����n�R���� S,�S.�iw ,/* m, S+�S,� S.�K+

��w /** m���� &)�� GPS����~������ ¡¢£���&)¤¥) {¦§¨bh|�Datamark LS2***SH} {©ª�«¬� +330} O_mA�­>®¯>?�� . ms, �°� +0 bit�q±~²�³����n�R�������´Oµ=�¶ GPSO_mA

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..

·¸§O^kC¹¨�yº»

¼ 73 ¼

Fig. ,. Seismic traces along the observation line for (a) S+, (b) S,, (c) S-, (d) S. and (e) K+. The vertical axis indicates a

distance from the shot S+ and the horizontal axis denotes travel time.

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����� ��������� /* m�� ����������������� Table ,�������� ������� � !�� �"#$%&'(��)*� ,**-� 3+ ++ +, ,�� /-./01�� 2�31������ 4�56��78����9��� CD-ROM�:;<=>?@�������� +++���2�ABC�DE�F��G�HIJKLM�NOP� QR�AB&S��

-� ����T����(UVW�"�X2�& Fig. ,�'(� YZE S+�����[/\�/� ]Z���,^��_`,-&OS:�X&�a:bU� c1d12��Tef�gh�i�/jkl��� T���Hm:� G���E�n/oUE� S,/�KLM��E���pqU�

-�+� G��NOPG��NOP�� 2�ABC�D +- /rS

�� TVEst��NOS�!&;u�� hv�NOP!&�"��� wxyfz�{G�#|}EP~3&u$�:� �NOP!��7�&%<��� �7�A

��NOP�&E�+* ms�'/bPG���E�[U�� �7� B��NOP�&E�-* ms�'/bPG���E�[U�� �7� C��NOP�&E�+**

ms�'/bPG���E�[U�� �7� D��NOP�&E�+** ms�'/bUEG���E(��/bU� [�� �7�A�D��/G�)*E�+/oU�&�7� L� G�)*E�+/orm� (00|� G��NOP!E,m�&�7�X@��� �KG�AB�-mU�@E�.U�7�A�D

�NOP!�� S+/ -/*�� S,/ ,,3�� S-/ -+.

�� S./ -12�� K+/ 23�/bS�� K+��(U�NOP%E�/��rm�� �0��/�����"�j1E�3�S���@uq�1U� �1���& Table -�'(� [�� c1d1����(U�,&���e���& Fig. -�'(� 2����%��,���o�� 3��"��&���(UE� S+� S.� K+%�� . km�s4&/bU���:� S,HIJ S-/� ,./ km�s4&@rS:mU� �1�� 5���67 E� ¡¢7 IP�"��&8m /901:mU�@&'£�:mU�

-�,� KLM�NOP�¤¥¦:§/�� �X�KLME���p�1��@IP� c1�&�NOS:� KLM�NOP!@�:[@�U�@����

S,�H¨U��¡;���/�� KLME���N�1U� �1�� ��@�,��������:HP� ���IS:<©31� S�{7=�ª>�EbU� �NOP�� ?P«S�����X&;u��HIc�+** ms�'/KLME�"/oU�&�N@S�� ��& Table .�'�� S,&¬­��:�,&���e���& Fig. .�'(� S,��N:@AB® / km%����� �XE�¡�%¯���@C¡�%¯��� ,°D�±�:mU�

S./�� -$���A²$�KLMEp�1�� Fig. /�� -$���A²$�X& S+��\�³��a��/bUE� E´/'��µ-�KLMEp:O1U� �NOP�� ¶F�A²$�X&-m�?P«S�����X&;u��HIc�+**

ms�'/KLME�"/oU�&�N@S�� ��& Table /�'�� S.&¬­��:�,&���e���& Fig. 0�'(�

.� ���5��²G²�A@A�]H(U·�/VW�":§&¸¹��� º�6IP»m�&¥¦&����(

Fig. ,. (continued)

5���H¨UVW�":§

¼ 75 ¼

����� �� 21 km���� ���������� ���������� �� !"#$%&'()�� *+!",(�� -./01&� 23�456789:;< =>1�?@)6�A�&BCD)�� E�� FGH/IJ=KLD)� M/!"#$%&

'()�� A)( ��NO/P�QR�� S/TU�VWX��

� �YZ[ \]X����^� _`/ab.�Tc/c

Fig. -. Travel time plots of first motions for each shot. The vertical axis indicates travel time and horizontal

axis are a distance from S+.

Fig. .. Travel time plots of later phases for S,. The vertical axis indicates travel time and horizontal axis are a

distance from S,. Times are reduced to 0 km/s. d indicates first motion. e, f andgindicate later phases.

hi j k

l 76 l

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Fig. 0. Travel time plots of later phases for S.. The vertical axis indicates travel time and horizontal axis are a

distance from S.. Times are reduced to 0 km/s. ¸ indicates first motion. ¹ indicates later phase.

Fig. /. Seismic traces of east-west component along

the observation line for S.. The vertical axis indi-

cates a distance from the shot S+ and the horizontal

axis denotes travel time. Later phases are identified

between arrows.

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CD E�F�GH��0 I�JKLM�N�OM�P�Q�R�S2�TU�V�W1����XYZ�[\]M�>^S_��`ab� ,**.a� bcde�fg"���hij��� !� kldm� no NO. .2� ,-�,0.

CD E�F�GH��0 I�JKLM�N�OM�P�Q�R�S2�TU�V�W1����XYZ�[\]M�>^S_��`ab����bcde�� !pq*4� ,**.b� ���hij� ,**-rbcde ! : s�t

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CD E�F�GH��0 I�JKLM�N�OM�P�Q�R�S2�TU�V�W1����XYZ�[\]MB >^S_��`ab����bcde�� !pq*4� ,**.c� bcde�fg"���hij�d��� !� �X���A ,**.r&��>A����� 3.

��S�� +31+� ���d�� d�� ����~���!���� ������A�� +�+.3.

N�OM�CD E�F�GH� ,**0� bcde��"��������� �Xdmz{��}~ ,**0r>A� U*/+�*--.

�Received September +/, ,**0��Accepted October ,*, ,**0�

CD E �

� 78 �

Table ,. Locations of observation points. The coordinates are presented by WGS2..

����������

� 79 �

Table ,. (continued)

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� 80 �

Table ,. (continued)

����������

� 81 �

Table ,. (continued)

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� 82 �

Table ,. (continued)

����������

� 83 �

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.

�� � �

� 84 �

Table -. (continued)

����������

� 85 �

Table -. (continued)

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� 86 �

Table -. (continued)

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� 87 �

Table -. (continued)

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� 88 �

Table -. (continued)

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� 89 �

Table -. (continued)

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� 90 �

Table -. (continued)

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� 91 �

Table -. (continued)

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� 92 �

Table -. (continued)

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� 93 �

Table .. Arrival times of the later phase for shot S,. Table /. Arrival times of the later phase for shot S..

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� 94 �