ῒΐ  .3  (,**.)
 0  -//ῌ-0/ ῕ ῔       

,**.  .  ,2  ,**.  +*  +. Three-Dimensional Seismic Wave Velocity Structure around the Hakusan Volcano
Naoki TAKAHASHI῍,῍῍, Hiroaki NEGISHI῍῍῍ and Yoshihiro HIRAMATSU῍
We determine the three-dimensional P- and S-waves velocity structures around the Hakusan volcano in the
Ryohaku mountains area, where there are some Quaternary volcanoes, using the travel-time tomography method.
We use +*.,10. P- and 31,,-, S-waves arrival time data observed at /,+ seismic stations from -,3-* earthquakes
in and around this region. The initial model, hypocenters and one-dimensional velocity structure, for thethree-dimensional inversion are simultaneously determined by the Joint Hypocenter Determination method.
Since dumping parameters and iteration number a#ect the absolute value of velocity perturbation, we determine
these values quantitatively by applying “Cross Validation Technique”. A checkerboard resolution test is applied
to the dataset to examine the resolution scale of this dataset.
We ﬁnd a velocity anomaly zone with low-VP, low-VS and high-VP/VS beneath the Hakusan volcano at thedepth of +* to +. km, while there is no such a region beneath other volcanoes in the Ryohaku mountains area.
Seismicity is shallower beneath the Hakusan volcano than beneath the surrounding areas and no earthquake occurs
within the velocity anomaly zone beneath the Hakusan volcano. These features support that the velocity anomaly
is a partially melting rock matrix with high temperature. The Hakusan volcano is one and only active volcano inrecent *., Ma in the Ryohaku mountain area. This geological feature is consistent with our tomographic result.
The existence of magma body, which can be shown as low-velocity body, may indicate that Mt. Hakusan is still
noteworthy active volcano.
Key words : tomography, Quaternary volcanoes, Hakusan volcano, VP/VS+ῌ ῐ ῎ ῑ ῏yz{|)}jn pq 6~y{AB#:G C-n6~y{)G $%&'()*+,-.'(/01

stuvaVW)ijFRMN1gYAB 



!

"

23 4567589:;<:.=>?@AB

Hirahara et al. (+323) @ P oq)G

C-?)DE,FGCHI@/01-J K9): /* km, \: -- km -

LK9MNOPHGQRB S"'(T@U

5:

LVW23C,XY@AZ [:.-\ S:va?)F C-,FG

VW)]C, ^--_3-.`a)bc

-"va-,FG K:,dGce>MN-fg@AB

Mikumo et al. (+33/) Jh-ULVW)ijklm-fg:
nopq)rdGstu9:novaVW nwx
 £3,*ῌ++3, ¤&¥¦§¨©ª«¦§¬K¬K­®¯°KMN°
Graduate School of Natural Science and Technology,
Kanazawa University, Kakuma-machi, Kanazawa,
Ishikawa 3,*ῌ++3,, Japan.
 _3 : £-3,ῌ2/++ ±¥²¨³ +ῌ,,ῌ-*²¨´Present : Suwa City O$ce, Takashima +ῌ,,ῌ-*, Suwa,

G{)OdGB ^-L-23)

GB IRP oq)G !

#:¡IHR !?-\ +* km I@-stuvaVW)ijFRB ¢X: ,* km\

Nagano -3,ῌ2/++, Japan.
 £-*/ῌ***0 µ¶¥g1 ¨·¸¹ -ῌ+º°K»¼MN´
National Research Institute for Earth Science andDisaster Prevention, Tennodai -ῌ+, Tsukuba, Ibaraki-*/ῌ***0, Japan.
Corresponding author : Hiroaki Negishi
e-mail : negishi@bosai.go.jp

]KºNO»*BC¼

356

 - km 
 





 

  

 1 km    !

"!#$%&'() *+,- ! Matsubara et^_ 
!+7

P uL)(! - 7  S uL)(;vw>^1$%c

Hirata and Matsu’ura (+321)   t)(%¡¢. ^_ n,- !uxyz t;,**, /7n?7,**+vw>{

al. (,***)   , ./01&$% 23 £ |} D= ,*** /7 !

234567~¤:^1d



!

1"#$%856

9&

 '$ . km  +/ km (+):; * <(=> Watanabe (+33-)?+&\n9&!¥tD<_ 23 £$%k! K HR>AB¦ / km kJ $% ,0 £$% H ,@ 4AB &-.() /** km  7 < %§¨ +** km  +/ $%7 01C 2D8563

kJ  0- £ & vw>2! P u S u©1ª1

4  ! E56789:D;<) *.*,I*.*/  *.*.I*.+  &> ©%¡¢.«

=FDG> H?@$ : AB *.,/   /I¬!AB ­K©1ª1 *./ km, *.- km  &+/ kmJ -.K7D>LL& HCMNO ,**-JPDEQ /* km R>d)$%c(! P u S u

! ,*** /R>FSTGSSUVvw>856 ®d ¯C¤ {856°t

H;IWXY & HJ ,,1*, mJ K$%¡VH!®d %¡856{ ©t)

%ZL M[\$%7

H]N ,**-J

O/^_() YZL!`<

P -*I.*

Q/Ra_(=> SbTUcVDd(7 856 t)R>   uxyz1D> $%B59& y97;;! 1*0 / +*., / +/.1 / +//. / +/13 / +0.* / 856 ;\®d ¯C¤ {+0/3 /WYZLefg 1 Hh +32* ; %i

856dt) 856w!n! +331 / +* / + I

XYMjk +32,J 1 SbTU=RlY ZQ,**, / 3 / -+ / / 856±!²:,-<  [m (,***) !YZL!P ./*-../I-1./  ³ +-/./I+-3   /** km / HZLn +**I+/* / o\ -** /J  n]&&> ± $% P u S u¤ { w() SbTU*pWY +0/3 / &>

> b1 $%c(uxyzD[q:ro\n -** / st(YZL^)_`´¯DR9&a)(=> !buvwAx^LL&K



7]& |} y\?@z$:D${;@|}BA cd$~e6Q:,-!1 d)L<D1(=> _;@|}BA< || 2L)(D

*.*/ µ*.*/ µ/ km wy¶ ©? ¤ *E$%?<&$% |}

+/ 7

;

+L

vw>

-,2.+ v·}B®d ¤856 t)
R(|}1$%! -,3-* £ Hf1() Hgt Honda and Nakanishi, ,**-) $%7 ®d J&> P u S uvw>< hzz HNO +330J ' (Matsubara et!©1ª1 +*.,10. £ 31,,-, £D_() ®d1()RD ||i>v45

¤ {856 !vw>2d*1(=>}j ${kl:mD.5A cd

7 u'¸;>* H I-impulsiveJ 

al., ,***)=FG>,-! L)(!D1()

HDJ * H E-emergentJ  - LyD) n,- ! $%B59&R>

1() $%B59& !vw /* km (+ bG> -.>2¹«¬ t P uvw>2!©

ZY(q:RD_()<1ª1 *.*,  *.*/  *.+  S uL)(! *.*.

;  G> yo$I
WXYL)(d;

 *.+  *.,  $%7 856
vw>2! P u S u©1ª1 *.*,  *.*.  /* km 856L)(! *.*/  *.+ ,ῌ ῏῍῎7 n?$%L)(! r)7 
8567

856

Hq@rs +33,Jp WIN 2t)( P u S uvw>

 n,- t)$%%¡yz

Fig. + ;n,- ! 7  H2 Jy\ /,+ 7 

856 ¥t  @${*;@|}BA ux ;\  R>

> QEF34RG'HI

 -* km   

 <=>?7@+/0

!"#$% +* km &'() *+,-#$% ,* km &'
12

357

./0

34 56 Fig. , 78 9 :;#-ῌ ΐῑ῏῎ῐ῍ῒ῔ABC12/0DEFG'HI JMA,**+ J

Fig. +. Distribution of the -3-* earthquakes used in this study. Stars (O) indicate the hypocenters observed at
the temporal seismic stations around the Hakusan volcano. Pluses (P) indicate the hypocenters reported by
Japan Meteorological Agency (JMA).

Fig. ,. Distribution of the seismic stations used in this study. Stars (K) indicate the temporal stations installedaround the Hakusan volcano. Solid squares (L) show the permanent seismic stations operated by Disaster
Prevention Research Institute, Kyoto University. Inverse triangles (M) show the seismic stations operated by
National Research Institute for Earth Science and Disaster Prevention. The total number of stations is /,+.
Shaded part in the left ﬁgure shows the highland area higher than +-** m. Open triangles (N) show the
Quaternary volcanoes in this area (KYO ; Kyoga-dake, GANK ; Gankyoji-san, MARU ; Maru-yama, DAIN ;Dainichiga-dake, BISH ; Bishamon-dake, WASI ; Washiga-dake).

¢¶S·¸¹ºT » ¼358 ,**,  JMA2-A  






  

&-.(&# ABCDEF<'#-«g1C @¬ ' : &'#>  % JK !"   (+312) #$!"  % & '()*+#, ,

GHB;­  ABCDEF<'- ./ !0" (Aoki et al., +31,) #1/2$
" (Yoshii et al., +31.) 34567 89. # :  " ;<=

WX Zhao et al. (+33,)

% ;<=#$>  ?@: ABCDEF<'GH& 'I

 Negishi etal. (,**,) #$,  P H S H®!" N H"OP#®!"H"OP,%

:(L#M)*

Koketsu and Sekine (+332) #$ pseudo-bending , ?% ABCDEF<' '?GH&#N+M &  , -n«Q: M Um andOP?%: &QR ST#,-U V

Thurber (+321) ¯­°±f ²³<´#µR 

!"  JK
WXY (JHD) ,#$Z!"
M &[,!"   \$K-.(& /!#.(M0]^_<`a^,%Z bc# Kissling et al. (+33.) deCDf
VELEST &&-.(& -g

1h#$ij2#$3kl-#m4
nopM ]^_<`a^q#'IGH&  JMA,**+ r ,**,
!"

5 gs

 tu -** km v

w: JHD ,

0#M:# x^y^CzD{<='I#$Z | } 'n#A~<E?63M '#>M;<=A#$Z 7#

\Z G

H;<= 'IZ(L%9I
$ |: JHD ,8#\ 
$Z #T 9$#x^y^CzD{<= 'I
: RMS (root mean square)  - ]=~<a^# *.-. ; *.,- ;% !"   VPῌVS

 &&

Fig. - (a) #pMGH& -"  <= D<_<pM /*km >

<=M *.+ km ῌ s %Z '?'

pM<a^,@ 3tu *.3

AI& /* km 

t# ;<=B?#&%Z GH&CBu67

: &&p  %  rD
VPῌVS ?E ¡D¢ v '7£9#¤FC LGu  \%  P H S H-.(&O¥I +.1 < VpῌVs #JK ¥ (J¦ p  L@&§¨, ;M©#ªv67 (Fig. - (b))

Fig. -. (a) One-dimensional velocity structure of
P-wave velocity (VP) and S-wave velocity (VS)(left) and the VP/VS structure (right) as theinitial model of the tomographic study
determined by the JHD method. Dashed andsolid lines show the P- and S-waves velocity
before and after the JHD inversion, respectively.
The error of the velocity at each layer isplotted on the grid node represented by solid
circle. (b) Correlation between the resultant
P-wave station corrections and S-wave ones.

?¼?@O+
  

  ! "#$% &'

$($)* +,-(./01$ $
($2% 3)*41/  M)o ou v/00j/mnoB  Cross Validation method gInoue et al., +33* ;Negishi et al., ,**, ; C ,**-i  D)%

D#&' 0j/mnoBo ou7$./0 89$)%v/0 2]1J2DxE3]f)?@A *.*/  3

 D. #$D-0j/mnoBy $ 56 +,* km):;<=>

359# B *.+ C*., -) (Fig. .)% DD &o' !"E1$FG$ H I#

% P  S F G VpῌVs O+  o o

ou

v/0

J2?hD-2-()J$% KL&"E1$:;< '( M)uK*$% *"A:;<1$ N* D#Yu v/0 DI2DxD- J

O+P,=%'( (Fig. - (a))% %0j/mnoBHx)#$

Cross Validation method  h KLM 

$% D-M. S01T2$)* U

NOu v/0 f4Y#)M  #$)./0

V WX/M)#$Y#D-3$%- PQo:o"#)./0  R$x

-M.-Q/R'.

!

) LSQR .

v/0y4Y#)Z[  M56 \]*)* -$ V.t9p.- ^_;`/a/<bcU-de#7MbcU f S KL¡$7TNU2Iz#$) g8he Inoue et al., +33*i% :;<=> A

.% D. VWI¢£ (ABIC (¤i -XY

 *.+ -)% jk:l/mno- #$)M9¥¦§ NR$§¨©]]Z[

qr *./ s:V.tu v/0 w;x

M ª*--X\)* UV WX/

 (fy D qr *./ -$ $ze(¤](^_ N«2% &'{|;}~o/ (f$ g +33*i% HM)I#)./0¬;U  `Ba &'^_;`/a/<bcUZ[<O+=- : + 7­ b®./0¬;U1$ op 

7s: 1/ῌ > ?h)O+,./ῌ

o0j/mnoBO+ ª* 3O+s:@$E1$ 56-M¯®./0¬;U R$x -$° -f)%

w; A*%Vp, Vs, 0j/mnoBNG 4)* P

 S o ou v/01$
±% +*ῌ 0j/mnoB1$

+ , - .

+ , - .±%%+* c² d¨ +,*** efFz:;</^ $ o oy 0j/mnoNG ª*)%
Z[

Fig. / Gx% R$§³G ?hN( P  S o ou v/00j/mn
oB  3#´# ,ῌ -ῌ 2 -(f)% &' Do ou v/0-0j/mnoB #$
UV WX/M) f)%
0 
0ῌ+ 

P*"yµg P  S ¶LZ[ 3#´# Fig. 0, Fig. 1 Gx% UV WX/M)b¯h·¸ RMS
Fig. .. Conﬁguration of grid nodes in horizontal
view. The grid spacing is *.*/ degrees aroundthe Hakusan volcano, and *.+C*., degrees forsurrounding areas.

º Variance reduction
:;<=>*.,1 i]Y *.+/ i¹

0+...ῌ -(f)% ?@*.*/ ]Y *.+ )E¨©

f) Z[->u0/oH
»Y#(]f)% &'  UV WX/MµW¶·¸¹º3·»¼360*.*/ 

 ! "#./# $%&'(')*+01
km 230# 

*.+  +. km 240

5

km 230 

67

:



+*
*.,

,*-* km {0;# Q

49 ,1./i-0./ km<,$S 0wx"~*.+  : ;  <#Dwx"~ 10k# C 

<

6}49 *i+. km 01wx"~%

D EF# <G * kms: ,lm1 &0k#

U01CVW CXYZk  66 1

k  962  (KYO) , 6 (MARU)   6 (GANK) '( (BISH) j)


|

J 





  (DAIN) * (WASI)  6¡IRo6[J \]

; (Fig. ,)# o6 ¢£+¤0 ,/ 

# Q49 +. km 01 *.,  : ; ^2401 : _R# 
*.*/ 



49 +2 km 0,#19R,wx .
.#  49 +2 km 2401 : _

B'MNO P;QR# ST 

jkRF# 49 +*i+. km wx"~jk91

01CHI ,<<JK $%&'('L1 ?@ 

81 49 +*6 -=>?@A'B  

#19R 49 +*i+. km$%&'(')*+ ,-Fig. 0, Fig. 16}wx"~149 0 km U0

Fig. 1)#`a1-?@U4 6 j) *  66 '(6<# ¥¦1 3*i-0* -+¥§¨o60 ῍.©/0o61

9 +* km 2301$%&'('LB'Mbcª«s ¬¦1 0* -+2­

RN/# < -?@de9f0; 1 $%&'('LB'MN_# Fo6 x®¯ (Fig. 0, Fig. 1)

gh0149 +* km 230 

QK©/0o61}49 0i+* km 01 P  S v+*i+. km 0 *.+  49*.+i*., ,jk81lm; :n! "#
6o6G01 pqG   !rs ^tu49 * km 0 P

 S v wx yz/ῌ {|. (Fig. 0,

x"~


¢£9o60. 6o61 ª«# F# tu ° 

49 0 km 01+*+* km {bcjk P S wx"~ yz-ῌ {| ;#6o61 

1 o61 ±F²³x1´29
# ©/0o61

660o6} wx"~Fig. /. The prediction error obtained from the Cross Validation method. The optimum values of VP and VS
damping and the iteration number are found at the minimum score, ,ῌ of VP damping, -ῌ of VS damping,and 2 times of iteration number.

Fig. 0. P-wave velocity perturbation (upper) and the checkerboard resolution
pattern (lower) on the eight sections in depth. Note that the perturbations
are measured from the average velocity at each depth. The Hakusan
volcano is indicated by a solid triangle (῏). Open triangles (῎) show the
Quaternary volcanoes. White pluses (ῌ) show seismic stations used in thisstudy. Seismicity is also shown with open circles.

Fig. 1. S-wave velocity perturbation (upper) and the checkerboard resolution
pattern (lower). All symbols are the same as those in Fig. 0.


361

·<¸µ¹º»uµSvw¼

362

     !

2*"#$-*% &'( Shimizu and Itaya, +33-) *+

,- .*%/010
234*56 78 0109:;<1=>?@A "h3%

, & $ +*+. km) N4WJX 56M,/EMOY

ZM/E*C'

HS!"



(Fig. 0, Fig. 1)  $ +*+. km "k, lWNd56M *+4A[ \9' "

B'%!%*C' D/E

#FI$$ /)  VPῌVS ,M *+,F &G $!"H,km #FI$$ /)Fig. 0, Fig. 1 %

*

$ +*+. km +8 VPῌVS ,[7*k7^_ $

2 %J K& L'F*M`"010(ANOI$F %! .PQ.RF*)S*TUF &AL'M%VW) XYZ;$  ([\]+A

 * C]

*C'a_$ 7bDM Fig. 2 9m &n)  Fig.
0 Fig. 1 *%cs4



<u"

L'^,_*, `$M/E=- 56s4 ?@!" (Fig. 2)

 &- , .a/) ([\# OI$$ /F 

 S 4,*v%"*MK&0M/E* - - .

4bc/Nd1eFI$2 OI$M/F*fgF* h3%ij#$ %+//E
B*k$ * km P 4

56M6+ $, ,7
9o:;Qp.Fq@r s4*$ /4 t4<k<u"=-u"=- !%4B 56M

 9/ s4* S 4,v%

*we8 e![\%$ JKL+fg¡N4

([\TU B s4*Nakanishi, ,**-) [\*%c4

<u"=-AN£/E!$ % <8K&xb

q@r

0ῌ, ῏ῐ῍ῑ

M /    ? +  A z B { (BISH) | } ~ &$ *0 km)%[$¤/E4 ¥x$

ijM Ne!sk¦Z; Alm
Fig. 2 2 ?@!"2 9tCD* EF
 P 4

+8 VPῌVS !

Nd% G#=ZM HHIo%

VWJB KL

 <k4¢+fgMNO M+M ([\u"=-AN(GANK) 

*h*%]+ &S 4  +8 VPῌVS ) *we+ %J ]+*"*w1

 y>?@!"Nd%

-d<u"=- 56s4*]+$  &'( Nakajima et al., ,**+ ; Honda andlWNd56M

 9/ $ -0./ km 82M/9m &n) 

4K

9/ VPῌVS <'/q@r0ῌ- ῎ῌ῍ῑsk-§¨©/no!"2

Fig. 3 

82M/n+ª (MARU) |}~(GANK) «¬{ (KYO) |}~*«¬{­EF Dp &-ῌ P)2M

$ +. km =-  k+1q*C' 

 (Watanabe, +33-) Nd%M!F,ªk #   y>?@

2MNO  $ 7 Kh3%!"D*h3 %

P 4 S 4 &/ῌ P)  $ +*+. km M VPῌVS Qc!%,R$HST ,*-* km /1 km





$T

 $Z@@;TU (Fig. 0, Fig. 1)

B4HST ,* km,$T / km PAN /EUVO8 KLp%"*M |}~ &Fig. ,a/) <k" 
%! ,**+*°

 ±^ ,**,&³´µQ ,**-)

"$rp%4)S* ®s$ /4¯

²6 /%c)S*
Nd%M/"®s$ Jt ¶5p%"

*'



"* VPῌVS *D (Fig. 2) N <k",]+ B* S 4! VPῌVS$ */ km =- 56 &A-A῍!"H*.*/ k?@!" (Fig. 2) *%ct 2MFig. 2. The perturbations of VP, VS and VP /VS on the north-south cross section
across the Hakusan volcano (along A-A’ in the index map). Red and blue
indicate slower (higher) and faster (smaller) velocity (Vp/Vs) of seismic
wave, respectively. Seismicity is shown as open circles. Low-frequency
earthquakes identiﬁed by JMA are also shown as open stars (ΐ). Mt.
Hakusan and the other volcanoes in this area are shown as a solid triangle
and gray triangles, respectively.

Fig. 3. The perturbations of VP, VS and VP /VS on the east-west cross section
along B-Bῌ in the index map. All symbols are the same as those in Fig. 2.



363

J¸q¹Wi8W"_sº364 



    ! ! "#$ %& ' ()  *+, )-

&./ 0

1 2,
1ῌ ῎ ῍ ῏,**+3,**, 41,56671,

89:;<=>?@A89:&BCDE?$ &42,  1,$,* km )

km %!"#F *.+3*.,  $7#F /( G+*3+. km H&'(I! VPῌVS JKL 1, 
(I&)M!B (O%(N< '(I ( 1 

&./ )-

P*71 2, 1  Q+, -NB.R)SP*71B T ( UV/W0RV/1XKL12/ (Y  3Z[\45!B

56&]2B$ 7

8



2,
ΐ

ῒ

9^_ =;<:;`V<Yab 1,>?@A89:&c7dB=, ef g>h?@V iA@V B>@V Bj@V Ckl@V
jD@V J@V Qm@V noE@V FG4H
IJKp`Vqr^_s FG4HIJtuLvqr^_s BjD Mwx NOPxyQ V^_s zR{ hS`Vqr|}:9N<=~  !B
T!a a, XU4V>W" 2X
 Y@Z  [.}
&, 9\:]. (2, )#
$,!aῐ῕῔ῑ
Aoki, H., Tada, T., Sasaki, Y., Ooida, T., Muramatsu, I.,
Shimamura, H. and Furuya, I. (+31,) Crustal structurein the proﬁle across Central Japan as derived from explosion seismic observation. J. Phys. Earth, ,*, +31ῌ,,-.
Hirahara, K., Ikami, A., Ishida, M. and Mikumo, T.
(+323) Three-dimensional P-wave velocity structure be-neath Central Japan : low-velocity bodies in the wedge
portion of the upper mantle above high-velocity subduction plates. Tectonophysics, +0-, 0-ῌ1-.
" 2X (+33*) ^89:  - E?
, .- ,3+ῌ-*0.
}9}IHirata, K. and Matsu’ura, M. (+321) Maximum-likelihood
estimation of hypocenter with origin time eliminatedusing nonlinear inversion technique. Phys. Earth Planet.
Interiors, .1, /*ῌ0+.
Honda, S. and Nakanishi, I. (,**-) Seismic tomography of
the uppermost mantle beneath southwestern Japan : seismological constraints on modeling subduction andmagmatism for the Philippine Sea slab. Earth Planets
Space, //, ..-ῌ.0,.
Inoue, H., Fukao, Y., Tanabe, K. and Ogata, Y. (+33*)
Whole mantle P-wave travel time tomography. Phys.
Earth Planet. Interiours, /3, ,3.ῌ-,2.
Kissling, E., Ellsworth, W. L., Eberhart-Phillips, D. andKaradolfer, U. (+33.) Initial reference models in local
earthquake tomography. J. Geophys. Res., 33, +30-/ῌ+30.0.
Koketsu, K. and Sekine, S. (+332) Pseudo-bending method
for three-dimensional seismic ray tracing in a sphericalearth with discontinuities. Geophys. J. Int., +-,, --3ῌ-.0.
Matsubara, M., Hirata, N., Sakai, S and Kawasaki, I.
(,***) A low velocity zone beneath the Hida Mountains
derived from dense array observation and tomographic
method. Earth Planet Space, /,, +.-ῌ+/..
_`Wi8 (,**-) 4; # W;}  ¡9abcGd¢ ¡9 £¤  ,/ 3-2ῌ3...
Mikumo, T., Hirahara, K., Takeuchi, F., Wada, H.,
Tsukada, T., Fujii, I. and Nishizawa, K. (+33/) Threedimensional velocity structure of the upper crust in the
Hida region, Central Honshu, Japan, and its relation to
local seismicity, Quaternary active volcanoes and faults.
J. Phys. Earth, .-, /3ῌ12.
¥l)ef (,***) gh¦Kp
i §j@V¨k`V^_` ©ªl«[  0..ῌ/0.
Nakajima, J., Matsuzawa, T., Hasegawa, A. and Zhao, D.
(,**+) Three-dimensional structure of Vp, Vs and Vp/Vs
beneath northeastern Japan : implications for arc
magmatism and ﬂuids. J. Geophys. Res., +*0, ,+2.-ῌ
,+2/1.
i8 (+330) 4;¬ I m £¤ +2 2/ῌ3+.
Negishi, H., Kumar, S., Mori, J., Sato, T., Bodin, P. and
Rastogi, B. K. (,**,) Tomographic velocity model forthe aftershock region of the ,**+ Gujarat, India earthquake. In Proceedings of +,th Symposium on Earthquake
Engineering, ,3ῌ-1.
i8W_` (,**-)   ¡9­®NMA/¯9:°6/±no²³4; #; }´p³ £¤  ,/ 30+ῌ300.
µ¶·­WJ¸q¹WDr VW"_sºWk9»¼W

# ¡72¢£   (,**-) 

 ,**-  A*//.
Shimizu, S. and Itaya, T. (+33-) Plio-Pleistocene arcvolcanism controlled by two overlapping subducted
plates, central Japan. Tectonophysics, ,,/, +-3ῌ+/..
 ! (+32,) "#$ %&'( +,3ῌ+-*.
)*+ ,-.+ /01+ 23  +  (,**-) #456789
, /0
23ῌ3..
:;<= (+312) >? @789
7ABCDE
FG7 ,H IJKLMN ,0 +./ῌ+/+.
OP Q + RST+ UVW+ XY Z + [S\(,**,) ]^_7 `abc7defghijkl
mnop7d- q rN 0/ +,-ῌ+-..
Um, J. and Thurber, C. H. (+321) A fast algorithm for two
point seismic ray tracing. Bull. Seismol. Soc. Am., 11,
13,ῌ120.
sh t+uvw (+33,) WINf89
xyz

yijk

365

{ |}7~7  + 
FH
 +33, 
--+.
Watanabe, T. (+33-) E#ects of water and melt on seismic
velocities and their application to characterization ofseismic reﬂectors. Geophys. Res. Lett., ,*, ,3--ῌ,3-0.
Y (+32*) ~#7"#  2 2ῌ+*.
Yoshii, T., Sasaki, Y., Tada, T., Okada, H., Asano, S.,
Muramatsu, I., Hashizume, M. and Morita, T. (+31.)
The third Kurayoshi explosion and the crustal structurein the western part of Japan. J. Phys. Earth, ,,. +*3ῌ+,+.
Zhao, D., Hasegawa, A. and Horiuchi, S. (+33,)
Tomographic imaging of P and S wave velocity structure
beneath northeastern Japan. J. Geophys. Res., 31, +33*3ῌ
+33,2.
F H