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Seismic Pseudo Reﬂection Proﬁling in Shirane Pyrocrastic Cone, Kusatsu-Shirane Volcano
Tomoki TSUTSUI+ῌ, Shin’ya ONIZAWA,ῌ, 3ῌ, Takehiko MORI-ῌ, 3ῌ, Kenji NOGAMI,ῌ,Jun’ichi HIRABAYASHI,ῌ, Yasuo OGAWA,ῌ, Noriaki TAKAGI,ῌ, Atsuo SUZUKI.ῌ,Jun OIKAWA/ῌ, Haruhisa NAKAMICHI0ῌ, +*ῌ, Shin YOSHIKAWA1ῌ
and Takeshi MATSUSHIMA2ῌ
Shallow subsurface structure of Shirane pyrocrastic cone, Kusatsu-Shirane Volcano is discussed with Pseudo
Reﬂection Proﬁling. Pseudo Reﬂection Proﬁles are obtained from a controlled source seismic experiment in
September-October ,**- as a part of the Fourth Joint Observation of Kusatsu-Shirane Volcano. A signiﬁcanthorizon is deﬁned through correlation of the proﬁle with borehole logging data. The horizon is compatible with+*+*ῌ2/*,
 +ῌ+
Akita University, +ῌ+, Tegata-gakuen-cho, Akita
city, Akita, *+*ῌ*2/,, Japan.
,-11ῌ+1++ #$%&'()'(*+,
0.+ῌ-0 5!6-.78/01234
Volcanic Fluid Research Center, Tokyo Institute ofTechnology, 0.+ῌ-0, Takijirihara, Kusatsu, Kusatsucho, Agatsuma-gun, Gunma, -11ῌ+1++, Japan.
-
23+ῌ+.+3 AB;AB; C;D.)E: +1,,
ῌ+3 !"LM/0NFG-.OP/012
34
Sakurajima Volcano Research Center, Disastaer
Prevention Research Institute, Kyoto University,+1,,ῌ+3, Sakurajima-Yokoyama, Kagoshima, 23+ῌ+.+3, Japan.
.*/,ῌ*+*0 cdefghijk +.0 cde
@fg-.JKN
Usu Volcano Observatory, Hokkaido University, +.0,
Tatsuga, Sobetsu-cho, Usu-gun, Hokkaido, */,ῌ*+*0,
Japan.
/++-ῌ**-, 5!"w!sxy +ῌ+ῌ+ 5!H
I/0N
Earthquake Research Institute, University of Tokyo,+ῌ+ῌ+, Yayoi, Bunkyo-ku, Tokyo, ++-ῌ**-,, Japan.
0-*/ῌ***0 STUVW z{| -ῌ+ LM}[\/0N

National Institute of Earth Science and Disasterprevention, -ῌ+, Tennodai, tsukuba-city, Ibaraki, -*/ῌ***0, Japan.
1
203ῌ+.*. !"-./01234
Aso Volcanological Laboratory, Kyoto University,
Kawayo, Minami-Aso-son, Aso-gun, 203ῌ+.*., Japan.
2
9:;, <. ,ῌ/0.-ῌ,3 =>?@
/0?FGHI-./0JK1234
Institute of Seismology and Volcanology, Graduate
school of Kyushu University, ,ῌ/0.-ῌ,3, Shinzan,
Shimabara-city, Nagasaki, 2//ῌ*2.-, Japan.
3
QR-*/ῌ2/01 STUVW 5 +ῌ+ῌ+ XY
 1 Z6[\]^/0NH_`a/0bPresent address. Geological Survey of Japan, AIST,
Tsukuba Central 1, +ῌ+ῌ+, Higashi, Tsukuba-city,
Ibaraki, -*/ῌ2/01, Japan.
+*
QR.0.ῌ20*, lmnop qrstu
nop?FGHI-.vLM/01234
Present address. Research center for Seismology,
Volcanology, and Disaster Mitigation, Graduate
school of Nagoya University, Furo-cho, Chikusa-ku,
Nagoya, Aichi, .0.ῌ20*,, Japan.
Corresponding author : Tomoki Tsutsui
e-mail : tom@geophys.mine.akita-u.ac.jp      

2



a top face of Tertiary volcanic rocks as a substratum of Kusatsu-Shirane Volcano and is estimated at +1** m a. s.
l. in the craters. The horizon strikes NNE-SSW direction and dips eastward. Its dipping is not uniform andthere is a bench zone beneath the craters which strikes NNE-SSW direction. Seismicity beneath Mizugama crateris concentrated and the active magnetization region locates beneath the horizon. Other clear reﬂection events
within the substratum are also observed in the proﬁles but their geological correlation is not deﬁned. One ofdeeper horizon at +***m a. s. l. may correlate a sort of density contrast in Tertiary volcanics layer. Seismicity
along the traverse line tends to concentrate under the deeper horizon beneath Yugama crater. The density
contrast may constrain seismicity beneath the crater.
Key words : Kusatsu-Shirane volcano, Pseudo Reﬂection Proﬁling, Auto-correlation seismology, Logging, Controlled source seismology, Structure of volcano+ῌ ῏ ῍ ῐ ῎/  ,**.

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3Fig. +. The temporary seismic network for this study. Solid circles are seismic stations and open stars are shot
points. The top portion shows the whole geometry of this study with +** m interval contour. A frame in the
top portion indicates location of the seismic network. The bottom portion illustrates geometry of thetemporary seismic network with ,* m interval contour. A cross symbol marks a permanent station KSE.
YGM : Yugama crater lake, MTS : Mt. Moto-Shirane, MNZ : Manza hotspring, KSS : Kusatsu hotspring, YMT :Yamada pass, MGM : Mizugama crater, KKM : Karakama crater, YUI : Yumi-ike crater, RH : KusatsuShirane resthouse.

E !"#$ (,**/) %&'(  (&%/ 012 )*+,-*.

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 / (,**. b) 6 Appendix

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12 $J3\6_j,J45&*,6
K/klN7  / ,**.b 6 mnJopqgf,r+os8,ti95N0::9', Fig. , Ju/ vw9:
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NB|&N}CV9 \69LJ .ῌ+0 Hz 6oD
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A L*+ῌ*. L.*ῌ.. 6 3 -\6,?

Fig. ,. Normalized and band-pass ﬁltered records
for the analysis. The pass band of the ﬁltering
was .ῌ+0 Hz in order to reject S wave arrival.
“S” marks the arrival time of S wave which wasvery weak in the original seismograms. The
mark “Reverberations” shows the periods which
may include multiple reﬂections to be processed.

.A9 ;6@V9GO *.+ sῌkm 5>6fPQ6.E6m !,>yJGA"#A9T6, Fig. - Ju/ ;6f

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CV!"#$%4/LMNOP (,**1) Q-
%R78 SL%TIUU76VWXYZ[\]545$ CV 6῕῍῎῏ΐῌῑῐῒ῔
ῌῑῐῒ

3SI^GH _`J 45$6abc00$ abc00$defge3SI(hij%d78U32kSIJJGHIJ 45$  +311 2JU3

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9:7GHWy/XYz{|}q~ T s*abc0

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k`HIJ45$1;wW*%45$ CV+./ 6c00$ %c00$pqrv +./ 78U32kSIJ%

9:+,Uv2d3*3

45$

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Z[\3*U3%783^GH.  

#76 W9:B|
Zq  VFRC 3* TI ,**+ 2h3SL , gO KSW 3 KSE %
`HL P ,**0  UHGgOJ H;
¡!J"#¢£3¤¥¦3%§¨HL gO3
Fig. -. Peak semblance distributions within the slowness range of *.+ s/km for the test of verticalarrivals. Decay in the curve of NW array isfaster than that of SE array. The correlation
windows for the analysis were deﬁned for which
acceptable level ( *.+) of peak semblances are
kept.

;¥¦`HL¤©2ª«P (,**.) %§TIJ $¬g%76UHGgO­®;S¯6&
°H±Hg² L/0 no L*1 %³´`HInµ
UU76gOnu¶·no'e¢£ij¸G¹ºSL,º5$3s»g²nu
2s(S 3¼3s(2§½

Fig. .. Coe$cient of variation, CV of all the peaks in each autocorrelation function. Cross symbols are CV atthe peaks of the autocorrelation functions. Solid circles mark median value of CV value calculated in the *.+ sinterval window. CV increases with increasing lag time t. A deﬁned threshold CV+./ is marked.

    

6



!"#$%

 L/0 &' ( Fig. /c #)*+ ,- #./,-01223

45678,- (Fig. / a) 90: +.* m (; <=>45(?@%A(B@% CD

E! +0. m E#F CG H  I JKLM 2

CKNO#./,-(PQ,-R90 S!

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5#s,*M-ICr @%Iq Fig. /a 

Serra (+32.) #LN_Cwxyz{|}~I.

: +.* m EGHIfghbci/,-no#;M{xy x9$M!@

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(fghbci% GH TVῌ!.;M_!#

'0

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0GHC()*I _ P *G TV

1K,- 229G3

0  (Fig. /b) 4u *.+- 5E63 (¡#¢% G30 £=y TV #s,*M m L/0 #;M&' 

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229(¦38§@ 63#¨@q0,- 2

I9©M9 &'  £=y TV (_L

3( 129 @% _Gª«0 U (,**/)

¬!9°@CrA9$M(,**.) fghbci%

ab³´:µ¶#·;*Mm L /0 0\¸
1#¸;eLqrM :µm&(±1*M&!@q²

_!#*M

.ῌ+ ῎ῐῑ L/0 ῌῒ῏῎ῐ῍ KSWm KSW  x ­ W ® TV ! ¯ * M _ ! ! @ T   U

KSW

eK# 45¹8,- (Fig. / a) : +0. m
E#JKLMGH TVῌ0Gº»()@qrm L/0 90: +** m ,-* m 299

M GHº TV ῌ0,-I¢¼L% _./,-6,-

u *.+0 5#$K¼LM<£=y TVῌ#"*M 

456¹8<=>( Fig. /a # 456¹8<=>KeL% ( Fig. /b #)* m (Fig. / b) 4 (Fig. / b)  TV ῌ ½=01>L?@9$M &' TV 1 (Fig. / c) #0 TV ῌ

Fig. /. Correlation between pseudo reﬂection seismogram at the station L/0 and the borehole logs at the permanent station KSW. (a) Regularized sonic and density logs, (b) synthetic reﬂection seismogram, (c) pseudo
reﬂection seismogram at the station L/0. LT marks the logging start point. TV points a velocity decrease at
the top of Tertiary volcanic rocks (Uto et al., ,**.). HB describes the bottom of the hole.

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<=37>0-#?@.ῌ, ῎῏ῐ L*1 ῌῒῑ῎῏῍ KSEAB?6CDE KSE F(,GH .* IJI ; <KLCD6M?@?

+.* m N5OPQ#'+&,( RSPQ-TDU?V%&5W,3XYI5Z

HPQ[\]^_`a3 Fig. 1a  [\]bcdef3g>; <-I,hOij0-k_J%l=+&5Y=mn3 Fig. 1b o (Fig. 0) XYg>; <  (Fig. 1c) 6ACDE KSE3 Appendix pW Fig. 0 o+&g>;q ,** m rstCDr L*1 3o<? t* Fuv +ῌ+* wHxy!

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6 +ῌ.  *.*2.

wH?@-./%& I5[\]k_PQ (Fig. 1a) ?6GH /* m - +,* m#,?6PQ$%& TVῌFu , ¢£H¤"r#PQ`a3¥¦§u,( !"6 *.*,

 GH /* m £H¤"r6 « (Lava Bot-¨©I,(Kª !" TVtom) £H¬­-./%& 0&®¯£H¤"r LB -° Zj¡!GH +,* m £H¤"
r6£H#¤±I z{| (,**.) ²&} Q (Underlying Lava) ./%&? 0&®¯£H¤"r UL -° Y=mn (Fig. 1b) ?6PQ³«´µ¶#· * +1
Fig. 0. Equivalent incident waveform. Equivalent
incident waveform is derived through stacking
all Pseudo Reﬂection Seismograms.

:?¸¹º LB ¹º UL ´µ !"36»$-$¼'mn"½#o+&,(

Fig. 1. Correlation between pseudo reﬂection seismogram at the station L*1 and the borehole logs at the permanent station KSE in the vicinity. (a) Regularized sonic and density logs, (b) synthetic reﬂection seismogram, (c) pseudo reﬂection seismogram at the station L*1 (at ,** m west of KSE). LB marks the bottomof Kagusa lava. UL marks the top of a buried lava layer. HB describes the termination of the logging operation.

  

8  Fig. 0 

 



 b)  YGM  L..L./ "# $ L *1 %&' (Fig. 1 c)

! L.2L/- (Fig. 2c)  W  L-*L/- (Fig. 2d) 

()* *.+ + !(,-"..#/!  S  L .+  L -2 

1* 234563789:&;<=>?@A'()B@AC>D@ *+ ,-.

E/F# (Fig. 1b) >G

1J;<=>?@A0HC>9I(Fig. 2 e)  TV $  % 0

K= ;D;K9@ )* *.+, 2LM@A 5NOP c (  YGM  3452 L (L //  L

Q7R(23/167 +ῌ. "867HS;<T/3) )* *./ 2LUV 5NOP d# UL #WX7PY0'(K$1JHSZ

!9($*34[#  YGM : L/+L/1 ;<= N : L,-L,/  W : L,/L,1 '(\9
L .1 T"! L .2 5NOP d ῍9]^:_*M/ 

=`aAbc( $*;[#<'(Kd$ >%&'0He>;<=fCA@5NOP9\@g$>hi.K

jkl? m@HnAB $*oApA

0('@D(K=9 Bqrjst+(oA"# u%&'HCv,$H Fig.

0wxDtEHS;<=>?@A

2 S Fig. 2 yF(GHIxz$HJ,+**m >; ={Ae|}(%&'K%)*0 ~}(F5$D@L\ Fig. 2a, b, c,bdv5NOP TV 9u$MNTd, e (oApA N, E, YGM, W, S ,$HS a"!5NOP d =<O 5NOP@oApAF (d5NOPPQH

UV)*> L/0 (KSW) T RD@S@;e\A TV $+TU (,..3 km/s) D@ TV $J/ῌ+  TV

HVW; Fig. 3b S + Fig. 3a (MN.K>

5NOP TV XPQH\# b0
- \];<H

>CA+YaA<=V  Z[,**. ; ^[ ,**. ; _[ +3., ; [ ,**0 ;$  L /0  S @AE / F # (Fig. / b)`[ +32- _waH>F>>eS

IbYH5NOP TV O

;<= Fig. 3 c ( YGM ,$ (Fig. 2 c)(+)

H ,..3 kmῌs Hc=<dUe;eH D@ *.,>;C>
(,)$ L/3 > L/0 > (Bqrjstf9

kU;<=C>> $ L/3 ( TV 0w1J

km bEgh;>i b0 Lj>i >

 i!9>>eS
0ῌ+ TV 

=flt9 -*.* m mU>?@AC>`[ +32-  ?< nH]

TV $J !9F (Fig. 3b) "> TV $(o¡.>%&'(=fltp"89233;ῌ+4¢+;q£¤¥HS;<= C

3/1¦RaA<=>?@AC>D¢( +3., r§s¨=fjkl+¥$/aA@ $ L /1 T"! L /3 S@A%&'©Atjª«¢ _[ +3., >u Fig.

- !(BqrjstfT"!o0wH

3a¬­=>?<ev=C>

w(K® x¯2L¤¥9°®K¤¢9)B@A(-)

Fig. 2 yFSaAEy TV ±²z{9h_K=C>

 C a@G H$> TV $¤¥( C°¤¥(x¯+D@_¯D<3;ῌ+4

¢HS;<= C(^[ (,**,, ,**.)o 5NOP TV ($ L/1 ,$9Y;_¯2LH |>}:~³ Fig. 3a

VA<;X¢D<)* *.- +d®K G H>#+®´Oµ7n}¢I>E.\C> T"!$*]^¶g<5NOP
TV 9PQaA/ῌ,
Nakano et al. (,**-) "A· @9¸#¹js 

bsi9da ,**.** m %&,$ (Fig. 2) ('bce5NOP>;<= daxzHx¯jªº_$\>> Nakano

HM=`C>9I TV $"#0wUVet al. (,**-) @jsbsi9wa( TV

5NOPH bd '»$w"8;<T# `[ (,**.) '¼H5NOP b ( E  L *0  L +* (Fig. 2

]>½K®>e=fjklxD"#wRE

   

Fig. 2. Pseudo reﬂection proﬁles. (a) Line N, (b) Line E, (c) Line YGM, (d) Line W and (e) Line S. Verticalaxis represents two-way travel time in seconds and horizontal axis is a distance from the rightmost station ineach section. Intensity of apparent reﬂectivity is described with a color-scale at the bottom-right. Positive
reﬂectivity is shown as reddish color and negative reﬂectivity as bluish color. The regions of which absolute
reﬂectivity is less than *.*0 are white colored in order to enhance weak reﬂectivity region. Locations andheights of each station are plotted as cross symbols and their name are also attached just above the symbols.
(KSW) and (KSE) mark control points. Intersections of the lines are marked at the common station of eachpair. Signiﬁcant landmarks are marked as italic characters. The top blue band and succeeding red bandshow a zero-lag correlation and its side robe of each trace and are neglected in the following interpretation.
TV marks correlated horizons with the loggings at the control point KSW. Codes b-d mark uncorrelated
horizons. YGM and YUI mark Yugama crater and Yumi-ike crater, respectively. A and F mark the alteredzone and the intense fumarolic region, respectively.

9 10  

Fig. 3. (a) Signiﬁcant geophysical anomalies detected by previous studies. The symbol A describes altered zone
at the surface enclosing with an orange curve. The symbol C aligns the +3.,’s craters (Minakami et al.,+3.,) with a yellow line. The symbol F marks the intense fumarolic area enclosed with another orange curve.
The symbols A, C, and F are located after Uto et al. (+32-). Blue contours describe Bourguer anomary valuein mgals after Makino et al. (,**.). The symbol M marks horizontal location of a thermal demagnetization
region around Mizugama crater (Koike et al., ,**.). Red asterisks are epicenters determined by Mori et al.
(,**0). White dots represent locations of the seismic stations, (b) Altitude of TV horizon. Solid triangles
mark the seismic stations. *.*+ km interval contours are plotted against a relief map of Yugama region. (c)Depth section of the line YGM with the correlated horizons and hypocenters. Adjacent hypocenters within*., km from the line YGM are projected by open circles after Mori et al. (,**0). A broken circle with M
marks the spherical demagnetization region detected by Koike et al. (,**.).

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BC8DEFGH) +323 ; I ,**0 ; J +330 K8&

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UV -. 6 WH)*LM*:

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6&2&12&Z? +/** m RW-5\]^"D,_&`aC#

K:NcV /0 Fig. 3c de@-!"4f:gD,:h'(@:)i<7 g@!_&5

*9 Fig. 3a NV P"b!+,ῌ-.

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7r8!s9 (,**/) 87,tV
wl.: s9 (,**/) 8j/C<60j/-d~q C;, b$%!D9H d%V!7%98IlJV  0:; 127r!

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=xyz{ S-

0Eyz{C "FG PRSῌTremorG ,ND K  L+1 L+3 n5K-E
:LDwlCN: " -, (PRS) >|?@AB +* C}n5V

=xyz{:E" +* N-.

K:NV  V &2 3CD L.0ῌ

V OH@, TV W-.   @ O  H C " L/* n5K-! =xyz{:E

M +** N-.K,NV <7 =xyz{K-(+33,) ! +323+33+ &Z12AW 1** m <Z

E`a!P-DV-.K:NV

 /.-

0

+* Am QC
1,

 tR (,**.) !

+330ῌ,**- &Z&2+. -** m W 0** m <V L.0ῌL/* n5K"  <ZF 

Z ,.2 +*1 Am, OC 0 OH@S ETk CL};U!"   +323ῌ+33+ }- ,.* m  0;G0,C Fig. ++ ND L};U

+33, +330ῌ,**- }-M +2* m  V 0

0; !E7h'(D9

 (+33,) tR (,**.) :V0O@;Ud WTWDL} *.2 C  +./ C! TV '()* d }TW Fig. 3c N

K  :E&PZ`a!P}-,

V P5XrYd$%¡Z.!A¡

PK:[&-. 0:;de@4¢\DP£¤Z f]¥ :g@!¦&Z¡,-!80ῌ, ῕῔ῐῒΐῑ d

9 j/",C§O5:?

Fig. 3c NV P 5X YGM -!'() L

1ῌ ῎ ῍ ῏/+ 7r/-[^_`DK:- /0 &2A,**- * d ! L /1 7r&

? +*** m 7r.

j/a¨b

Cd"



W L.1 <= L.2 - d῍P©c0'()*:+ ?£ªV : " 7-,e-!

Cf0 5X¡/0!rY-f 0gh«i C

QD'()*:¬­5X-,®¯]°-8"±²C;0³´ -!

 5XrY-

D!" 3 µR¡: } L./L.3 AW ? +*** m RW  d῍RW - /0

? +*** m RW TV :

BV EF
V

G¡TWD0 TV !,-,l&;%9:e87 5X-,Z-¶j3 *.- C7rk  &

@lm0@-!"4fG·:g TV w¸!®n-89 &27r-"w¸:¹

wl:]¥ 98 &27r¹w¸o!++,ῌ--.3lC

Nurhasan et al. (,**0) !

7r ? +***

m 7r»sBC <7 K !:uv<Z'()* d #$ ?TWD '()*N K ! +3., ºV 0pq 3r3l
? +/** m 7r-

D5b$%t¼Il®uD "& !½

  12

 

Fig. +*. Power distribution in the network. Solid circles mark power of Pseudo Reﬂection Seismogram (PRS)
and open circles mark power of background tremor at each station. Open rectangles mark ratios of powers
PRS between and background tremor. Even above the weak reﬂectivity zone which is marked, PRS/tremor
ratios have large values.

Fig. ++. Comparisons of Pseudo Reﬂection Seismograms and autocorrelations of background tremor at the each station. Autocorrelations arenormalized with zero lag value of PRS in eachpair. Interference of background tremor on
Pseudo Reﬂection Seismograms is clearly negligible.

 !"#$%&'()*+, b, c, d-./01$2345 '()*+, b 6 TV 7
809:; <=>?@80ABC0DEFG '()*+, c 6<=>?@HIJ0KDEFG '()*+, d 6<=>?@HILM +*** m NO0
P4 <=>Q-.R#FSTU>Q/VWXY+,Z[,R\F]^_ `G ab<=>Q! +330,**- cdefghij6 TV 7kl8909:F

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Clearbout, J.F. (+302) Synthesis of a layered medium fromits acoustic transmission response. Geophysics, --, ,0.ῌ,03.
¨ (+311) ©ª«s1¦ §¨@b +0,.
Ct (+330) ~ m«¬ < - ==>>;;??@ C" 2 D / I+.
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Minakami, T. (+3-3) Explosive activities of volcano
Kusatsu-Shirane during +3-1 and +3-2 (part I). Bull.
Earthq. Res. Inst., +1, /3*ῌ0,-.
E# ghFijSk (+3.,) ~ m n o  +. ,+-ῌ,,1.
2 LCt#uv (,**0) ,-w9(;; x /+ .+ῌ.2.
Nakano, M., Kumagai, H. and Chouet, B.A. (,**-) Source
mechanism of long-period events at Kusatsu-Shirane
Volcano, Japan, inferred from waveform inversion of thee#ective excitation functions. J. Volcanol. Geotherm.
Res., +,,, +.3ῌ+0..
Neidell, N.S. and Tarner, M.T. (+31+) Semblance andother coherency measures for multichannel data. Geophysics, -0, .2,ῌ.31.
Nurhasan, Ogawa, Y., Ujihara, N., tank, S.B., Honkura,Y., Onizawa, S., Mori, Y. and Makino, T. (,**0) Twoelectrical conductors beneath Kusatsu-Shirane volcano,Japan, imaged by audiomagnetotellurics, and their implications for the hydrothermal system. Earth Planets andSpace, /2, +*/-ῌ+*/3.
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Robinson, E.A. and Treitel, S. (+32*) Geophysical signal
analysis. Prentice-Hall, ,/-p.
Serra, O. (+32.) Fundamentals of Well-log interpretation.
Elsevier, .,-p.
Tsutsui, T. (+33,) Pseudo reﬂection proﬁling method : ane$cient complement to the CDP method, Geophysical
Prospecting, .*, +/ῌ-*.
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