, - Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2+ ©,**1 pp. 1+ῌ3. ,b ῌ +ῌ+aῌ -ῌ.ῌ /ῌ/ῌ ῌ 0 ῌ 1 ῌ 1 ῌ 2 ῌ !3 ῌ "#3 ῌ $+ ῌ % + ῌ )* ++ ῌ ,-+c ῌ . /+d ῌ 01 &+ ῌ ' + ῌ (+ ῌ + + + + ῌ2 3 ῌ4 5 ῌ6 ῌ78+ῌ9 :+ῌ*+ῌ;< +ῌ= >#+e ῌ ?@*+ ῌ A< B3 ῌ % C3f ῌ DE3 ῌ F3 ῌ 53 ῌ G 3 3 ῌH% ῌ7 I1ῌJK1ῌLM1ῌH% N1gῌOP Q1ῌRS#,ῌ /I,ῌT UV,dῌW%X,hῌY,ῌZ[\+*ῌ]^ +*iῌ0 :*++jῌ _" `/ ῌ a b/ ῌ %c[\/ ῌ 8M/ ῌ d e/ ῌ f-/ ῌ g / ῌ / ῌ )hi+, ῌ Yj +,b ῌ kl 0 ῌ mI0 ῌ nop0k ῌ qr+- ῌ , s+-ῌ tuv+-lῌwx#2ῌyz [2ῌc {-ῌ_- |}~ῌ, | ~~!~ ῌ- ~!~"ῌ. ~~~"ῌ / ῌ0 ~~!~ῌ1 ~~!~ῌ2 }~#ῌ3 $? ~~~ ῌ+* |}~%ῌ++ &~!~"ῌ+, ' ῌ+- }~~!~ ῌa ¡}~~!~ ῌb ¡¢(£¤ῌc ¡ ~ ~!~ ῌd ¡)¥ῌe ¡*¦§&~#~"ῌf ¡|¨ ~ῌg ¡ ©ªJAL «¬®ῌh ¡¯ª°±²ῌi ¡³´µ¶·ῌj ¡|}~ῌk ¡ ©¸¹¶· ´µῌl ¡ + 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+ ¼ 71 ¼ » S 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 + J |G('} W hm~) J*Nm =*N -,110 m .** km- 167;$567 J |N O!G(' +$# ! +* "#$%&' J; , WP4c6 ()*+, - ./ + "#$ 0)123 4567 - ,**- 2 .#$ 3 c#< 8#$ 9:; 9: 6 0 /076v52 <$5= >? ,*** G(<'1 -; 2$52'3 @ῌA B+167 *2 1 CDEF ! +,* G: +* H IJ167= +1*1 L -** K 8« /9 X:¬ ῌS ,**.a ; M IJ167N7 O<6P7= ! QR -¡4 56;¢£¤ ¥9N] ¦l§ ¨ J5$¦l§#$2$5©ª 7 ῌS ,**.b ; ῌS ,**.c ; ;YῌS ,**0 =ST#$UV EWP7J; XY ,**+ *2 , Z[\N]^_`a 67 ®H'1< + ῌ@ = != 6+ ! @¯= bP4c617 X d +31+ ³9 , @'}´Az#$Bµ ef_ghijklm=!jklm;nlo^pj 3 ¶C3· klm"qrs7tu+ v$w#$%= J<E ¹ 2c Fig. + º XS+ S, xy&167'z XFig. + X{ +323 S- S. K+ ¨ ¼ 72 ¼ °v +* km >?* , ±²? ;!5$D¸9 J; / '56 12 56 ·¸§O^kC¹¨yº» 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.. DGPS GPS ῑ yz {Mark Products h| L-,,D} ~>>?Lr + m ῏ ! *.1 ῎B S+ ^_` K+ ~ῐ 21 km O^ " /* m # *+ _ 2O nR .03 R RO2 ,-. /0 +** mm 12 34 2* m 56 7 yz~ P 0+ RO^_` 0 ++..- mm, 84 ../ mm 9:.;<=)$>? Okyz~A - nR 4@ABC D῎,E /** kg F;!-῎,E nR S,S. iw ,/* m, S+S, S.K+ G,-.;H<IJK ῍LMNO,-4@ w /** m &) GPS ~ $%& ' (&) P@Q@,-RST U V ,-MN ῌ Table + OWXY65C ,-OZ[C,-.\ Datamark LS2***SH} {©ªῌ«¬ +330} O_mA ]^_`,-ab c῎defghijklm >®¯>? . ms, ° +0 bit q±~²³ΐ n oῌpqr , Hz, st(uvw ,., kx ¡¢£ῒ&) ¤¥) {¦§¨bh| nR ´Oµ= ¶ GPS O_mA ¼ 73 ¼ ῍῏ ῎ ῐ Fig. ,. Seismic traces along the observation line for (a) S+, (b) S,, (c) S-, (d) S. and (e) K+. The vertical axis indicates a distance from the shot S+ and the horizontal axis denotes travel time. ῌ 74 ῌ 5H¨UVW":§ NOP&E+* ms '/bPG E[U 7 B NOP&E-* ms '/bPG E[U 7 C NOP&E+** ms '/bPG E[U 7 D N OP&E+** ms '/bUEG E( /bU [ 7 AD /G )*E+ /oU &7 L G )*E+/orm ( 00| G NOP!E,m &7 X @ K GAB-mU@E.U7 AD NOP! S+ / -/* S, / ,,3 S- / -+. S. / -12 K+ / 23 /bS K+ (U NOP%E/rm 0 / " j1E3S@uq1U 1 & Table - '( [ c1d1 (U ,& e & Fig. - '( 2 % , o 3 E S+ S. K+ "&(U % . kmῌs 4&/bU : S, HIJ S- / ,./ kmῌs 4&@rS:mU 1 5 6 7 E ¡¢ 7 IP"& 8m /901:mU@&'£:mU -ῌ, KLM NOP Fig. ,. ¤ ¥¦:§/ XKLMEp1 (continued) @IP c1&NOS: KLM NOP!@ :[@U@ /* m S, H¨U ¡; / KLME Table , N1U 1 @, ! "#$ %&'( HP IS:<©31 S {7= ª> E )* ,**- 3 + ++ +,, / -./ 01 231 45678 9 CD-ROM :;<=>?@ ++ + 2ABCDEF GHIJKL M NOP QRAB& S bU NOP ?P«S X&;u HIc+** ms '/KLME"/oU e -ῌ ῑΐῒῐ S. / - $ hi/jkl T Hm ¯@C , °D ±:mU A²$ KLMEp1 Fig. / - $ A²$ ZE S+ [/ \/ ]Z ,^ Tefg & Fig. . '( S, N:@AB / km % XE¡% ¡% ¯ _`,-&OS:X&a:bU c1d1 2 &N @S & Table . ' S, &¬:,& ® T (UVW"X2& Fig. , '( Y : X& S+ \³a /bUE E´/'µ-K LMEp:O1U NOP ¶FA²$ &-m ?P«S X&;u HIc+** : G En/oUE S, /KLM E ms '/KLME"/oU pqU & Table / ' S. &¬:,& NOP 2ABCD &N@S e & Fig. 0 '( -ῌ+ G NOP G X +- / rS TVEstNOS!&;u hvNOP .ῌ ῎῍῏ !&" wxyfz{G #|}EP ~3 5 ²G²ῌA@A]H(U·/VW": &u$: NOP!7&%< 7 A §&¸¹ º6 IP»m&¥¦&( ¼ 75 ¼ hi j k Fig. -. Travel time plots of first motions for each shot. The vertical axis indicates travel time and horizontal axis are a distance from S+. Fig. .. Travel time plots of later phases for S,. The vertical axis indicates travel time and horizontal axis are a distance from S,. Times are reduced to 0 km/s. d indicates first motion. e, f andgindicate later phases. 21 km !"#$%&'( '() A)( NO/P QR S/T UVWX ) *+!",( -./01& 234567 89:;< =>1?@)6 A&BCD) ῍ E FGH/IJ=KLD) M/!"#$%& l 76 l ῌ YZ[ \]X^ _`/ab.ῌTc/c Goº»cd_= ! "# $%& '& (%# )*(+, -./ 01 2345) , 6 7 8 6 9:;8 < =>?@ ABCD8 E F;8GH IJKLMNOP QP GRSP <T U=HVVWXYZ [V\]^_=` 2 ab0cdefgh +/ ijkef [V\] ^_=` )l : mn ,**--A-+-, opqr0stu vUwxKef )h +-ῌ+/ i, [ Vy z{Kef|}~i` )l : Lo B, P H _=z! : _="ῌ : # B "U= : $ 6 $ !# %B # B ¡ ¢ £¤ : ¥¦§ ¨&©ª : «¬ !# ' m® Fig. /. Seismic traces of east-west component along the observation line for S.. The vertical axis indicates a distance from the shot S+ and the horizontal axis denotes travel time. Later phases are identified between arrows. ¯ ° ( ±²) $ %B b³²´ µ&*D ¶·+ : 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. ¼ 77 ¼ CD E ῌ῏῎῍ 1+ +, ,**+ +/3/ῌ+0**. ῌ +330 ! "# $%&' ()*+,-* ./ .+ +,1ῌ+-3. 012 +323 345*678698: -,- ; <= <=>?@AB CD E ῌ FGHῌ 0 I ῌ JKLMῌ NOMῌ P Q ῌ RS2 ῌ TU ῌ V ῌ W1 ῌ XYZ ῌ [\] Mῌ>^S_ῌ`ab ,**.a bcde fg" hij ! kldm no NO. .2 ,-ῌ,0. CD E ῌ FGHῌ 0 I ῌ JKLMῌ NOMῌ P Q ῌ RS2 ῌ TU ῌ V ῌ W1 ῌ XYZ ῌ [\] Mῌ>^S_ῌ`abῌbcde !pq* 4 ,**.b hij ,**- rbcde ! : s t uvw3xy ,**. rdmz{|}A~>A V*//ῌ *+3. CD E ῌ FGHῌ 0 I ῌ JKLMῌ NOMῌ P Q ῌ RS2 ῌ TU ῌ V ῌ W1 ῌ XYZ ῌ [\] MB >^S_ῌ`abῌbcde !pq* 4 ,**.c bcde fg"hijd ! XA ,**. r&>A 3. S +31+ d d ~! A +ῌ+.3. NOMῌCD EῌFGH ,**0 bcde" Xdmz{}~ ,**0 r>A U*/+ῌ *--. Received September +/, ,**0 Accepted October ,*, ,**0 78 Table ,. Locations of observation points. The coordinates are presented by WGS2.. 79 ῍῏ ῎ ῐ Table ,. (continued) ῌ 80 ῌ Table ,. (continued) 81 ῍῏ ῎ ῐ Table ,. (continued) ῌ 82 ῌ Table ,. (continued) 83 ῍῏ ῎ ῐ 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. ῌ 84 ῌ Table -. (continued) 85 ῍῏ ῎ ῐ Table -. (continued) ῌ 86 ῌ Table -. (continued) 87 ῍῏ ῎ ῐ Table -. (continued) ῌ 88 ῌ Table -. (continued) 89 ῍῏ ῎ ῐ Table -. (continued) ῌ 90 ῌ Table -. (continued) 91 ῍῏ ῎ ῐ Table -. (continued) ῌ 92 ῌ Table -. (continued) 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..
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