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 /  -0-ῌ-1/ ῕ ῔

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Magma Supply System of the ,**. Eruption at Asama Volcano Estimatedby Crustal Deformation Data
Akimichi TAKAGI῍, Keiichi FUKUI῍, Kenji FUJIWARA῍, Yoshihiro UEDA῍῍, Sei IIJIMA῍῍,
Tetsuya YAMAMOTO῍, Takayuki SAKAI῍, Tomoyuki KANNO῍῍῍ and Hiroaki KATAYAMA῍῍῍A geodetic observation network with GPS and EDM at Asama volcano detected pre- and co-eruptive crustal
deformation. Observed horizontal displacements by GPS before the ,**. eruption indicated radial pattern
outward from the active summit crater. An east-west baseline indicated secular extension with 1 mm/yr from,**, to the occurrence of the ,**. eruption. Rapid extension of +* mm was detected at the baseline near thesummit, which may suggest magma discharge into the shallower chamber.
We estimated the magma supply system from the observed geodetic data assuming buried two pressuresources. One is at a height of ,,** m above sea level beneath the summit crater (Source A) and another is +./km east of the summit at sea level (Source B). Our data indicated that before the ﬁrst eruption discharged
magma from the deeper to source B was ,**/+*- m-, and from source B to source A was +./+*- m-. Totalamount of increase in volume of source A was estimated to be more than /*/+*- m- by EDM and GPS data by
the end of the eruptive activity.
These small but signiﬁcant signals could be observed only in our network near the crater. Our results
indicated that dense geodetic observation near the active crater or vent could give important and interesting data
to clarify and monitor the active volcano.
Key words : Asama volcano, magma supply system, GPS, EDM+ῌ ῐ ῎ ῑ ῏01234- ,**. ( 3 ) + *567892:;<=>? @A925BC- 2ῑ4DE3FGHIJῌ 0@om3- 01ApZYhiqrstu5Bvwx
iyzy{|}A\]4- ~ (+33*) _54onin? `A῏῍492A012

km AKL5MN=- 9OPQ>2R4ῌ / STU3:- E '- ,**, .  'Y

VW> 'JXEYZ[\]^- ,**/a.? 01A678\]^ Z῏- ,**. . ABihk:

92A;<4 +32- (_῎3VW>? `Aa- - bA67

3Vv234inn@- m>- Da5;892cdefghi92jk:l( +, )m3gn>?

<=>678924 ,+ ( A@3- GPS ABi¡ ¢-*/ῌ**/, £¤¥¦§¨©ª« +ῌ+¬­\]^Z[2\]®
Seismology and Volcanology Research Department,
Meteorological Research Institute, +ῌ+, Nagamine,
Tsukuba, Ibaraki -*/ῌ**/,, Japan.
 ¢-23ῌ*++/ ª!¥I¯°±² ³´µ¶ ++/+ῌ,Karuizawa Weather Station, ++/+ῌ,, Oiwake, Karuizawa, Nagano -23ῌ*++/, Japan.

 ¢+**ῌ2+,, JX·¸¹ºE»´ +ῌ-ῌ.
¬­¼Z[2®
Seismological and Volcanological Department, Japan
Meteorological Agency, +ῌ-ῌ., Otemachi, Chiyodaku, Tokyo +**ῌ2+,,, Japan.
Corresponding author : Akimichi Takagi
e-mail : atakagi@mri-jma.go.jp

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G 4 , ¢Q ,**.

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3Q

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3 Q Z [ w x y z { dL<GX,+"8 Y 9#!

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H - 4D9

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'(@ HG<()*+  G
,-D9/0/123 e+f ",ῌ ῍ ῎ ῐ

9<

+ GPS <`%a(EDM) <\] " GPS < )*<^_$<8" )*<9Dfg

M+@h+9,Z;@8  ^_$<9i.jD/k F +8"  `%a< GPS <0l mnop1
q  9-+2r@ +b

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Q+ GPS )*<4 - 4 |C 4 KWS, ONI} 7
(Fig. +, Table +)" ~ +-8c9/0/12+& +@ L_9-+r

E, G 47c9 9-" wxyz{

G +./%-.* km a:+A9,

 C, E, G 4 - 4@ G9-_ L+;<c

 (Fig. +)" =< + i%>?w

MG,++* |@CA ,**,} @ mnovuv0
-* B |,**.

+* QZ[ +/ B} / +/ @A

" *Ck>?w CAP-Win, 6 "  YDD+F/k @MH+4 k9 + DE

Fig. +. GPS and electronic distance measurement(EDM) observation network around Asama volcano.

¬ +" D9 GPS ­®`%a<U" ¯° :GPS )*<4 |wxyz{} ¯± : GPS)*<4 |9«von} V° : GPS ^_$<4 W²° : `%a6X³´7!
GPS ^_$<4 Yµ : ¶·¸ |9«von}¼t95X ,**. ./1<=<>?@
Table +.

Location of GPS and EDM observation sites.

^ +1..++.+ km 

GPS `a EDM % 

 - 

 GPS O8'+%}~q XX  G/

A 6P APS-+; !" , #

$ GPS

%

%  (GEONET) *+,-

365

&'()

!

.#G.

G- @ :o -VX%  -IJ%

KH (KWS) B

CD 6?z+,*+/ m; + EFG HKI7J i/ +3,2 km 012345 /#+, 9  6,**. % 78 9:

23 0*** $ 6+ # $ K# L +..32.0/+ MHz;2+- km   ;,ῌ,/3

 :o f/; 1 km 

9

GPS ῐ῍῔ῌ῎ῒE$I7M%  78<=<>?@A  Q:o34R78 N  #!"B1C<3D#+
E$FGH 0123IJ%

KHL&

,**,  +  , MNO8'+%

6PQ1

R31% ; ST+,- (U+VW% )
+ %  ,**. 9: 2 %  XNO:oPi

S / -N k % L¡ ,**-  / e ,**/  - ef ,*, 
% TU /1f¢e 8 2 VU  /¢e 8 +, VUznm/-EI7hWXYZ8

Y Z*[ (G,) \+ (G0) \, (G1) P[ 9+ E$£32m\]^+,+]-^.%WXg¤ _-HB1C<3D_.+,-

 Table + `a Fig. + b%`a /b@B1C<3Dci :o/?z¥¦5-i

d %  ,**,  1 e/01 ,**.  1 e§,5¨©cdeª -  « 7fNg 0 ST+,-/ 1 km fk ?z¥; +,/** m --g,ῌ- ῑΐῒ῏῎ῒ2h+
GPS 76%N m\SE¬ E­-kh n b
i34j5 # k l789+

E$I7i±²j³k+m/%  n:opqr)#+

\!s,,+; + km 1t 6.,-Lmlng¤µ.5X=q¶~1·

 w,=

£32E$ZA i.¸¹.op+,WXu6<v

x>y; ?z ,,..*,,./* m 8.{ M+

M,

M-  - #|5X,-% h ®¥eª 7, E$WX78X¯ /¤°

; /** m-X´  -   E$BE$l  n`a.-

6zq¸ ,**/; º SῌN -r»s5X   t95Xij 9m

´µ¶µ·'µ¸µ¹µµº¶µ»µ¼

366

Fig. ,. Time series of the baseline lengths observedby three permanent GPS points from April to
December, ,**. with daily number of volcanic
earthquakes. Rapid extension with +* mm wasobserved at E-C baseline between ,+ and ,,,July.

j , GPS ªN (C, E, G) PQ<R,**. = ."+, K ¤«! STU HVW
1 K ,+ῌ,, ! EMC NLPQ defgh
78 AB£qSTU l¬­

+* mm

 / mm   !"#!$%&'()*+,-./

Fig. -. Time series of the baseline lengths observedby three permanent GPS points and daily number of volcanic earthquakes. The baseline
between E and TAK has an inclination to extend.

j - GPS ªN (C, E, TAK) PQ<
R ,**,",**/ = EMTAK LQ®
1 mmῌyr ¯°7t|}, ¤«!
STG1STU HVW j±²³
RHPQ<RuHVW  ,012 345678,9:;,<./
R EMG O8 CMG NLlpic^=.01>?@ABCDE{_a</|}~W,Ecxl-ῌ ῎ ῐ ῏ ῍-ῌ+;c ^ defgRuvic

GPS ῒῑ῎ῐ

il EMC NL1,^c

Fig. ,  FG1/HIJ ,**. = . K"+, K/L EMC NEMG N

O8 CMG NLPQ<R! STU HVW X EMG NNLYZ[O8 CMGG NH\] 1 K +0 !^_YZ[HU` 2 K +* !a

+ bK



kRi

 F

} } 7t2Wch,HV
W,

Vic,

kRW,_YZ[H:il mno]p(W, +, qL./01rsic,l defg1Ecl EMC NPQ  ,^ EMC N^c 1 K ,+",, ! EMC NLPQ<defgh
 +* mm 78ic, ja EMG NLl ^c EMC NPQS GEONET 2ST GPS 9¡H¢JPQci£ 1 K¤¥7t|} :;, N¡^,."-0W¦i9-/Ldefgh:;qLHi7tic,*^ G Nc a EMC NPQAB§<Q

KWS 

\]

EMC NLdefghRuv, / !_ wx

EMC NLdefgyzW,

ONI ¨]W,x

+©*,PQ CMONI, EM

KWS, O8 ONIMKWS Ll

1 :+

v PxCM ,**. '% D IJIKL­

367

Table ,. Step changes of GPS baseline accompaniedwith seismicity.

 , )5 GPS d4:



E TAK, C TAK, E C %d4:)EC /

 1  ,0        !"#$ -+
%



&'() + , *+,-Pu 

 + S%Qd4U.Ry ,/S%SSCFM 
 D . >-T;GPu
E TAK d4: - '%6 , cm 8cH./  ,**.0  1  

+ 'GHuMD 1 mm

8)PFMD

23  45)6789 

M U C TAK,  EC d4:

: 4 ; 1 <= > ./B  %GHZ$#VW;F  ,**.0  / ?@A%)X:& Y G

B CDE!"FDGH D; E TAK d4:HHC

4 ; IJIKL#$FDwM  Z FMD)NOPQFM  %RCE % / S%&THGDUVWDX

D|w M[ (,**.) MD

,FF,**/ ' - 4Y G  ,**. ' +, ()Z$#4[*CGM  +\F]Z$#[,FF)tZDM

,^;_

%

¢]B

\R¡ GEONET £¤ E TAK d4D^¥O% _`)¦d4^a89 ^;§bOB

CFM [ (,**.) Z)C<©d< +e- km ª%` /4ab01GMi«e:fgFM hi¬G (,**.) ;c %    D

2

_Ukm ¨cF()B  -Z$#[CU.C_FUVGM E TAK d4: £3 ,**- ' 0 D ,**. ' - ; EC "IJIKL­,)EwFb01Gd4] M (Table ,, Fig. -) SM56 /e+* mm 7f  ,**. ' 1

c/BjtquMplkl®¯GH

89Dg!"GM d4:hij&'(d4U.y;k<l ,e- mm mn)°¤ 

;k<l ,e- mm GM =mGM ¢m±o²^c  - >Sn?/@A>)6´FMb01;GM  B C8

c o /@AplBqDMb01F 4E!"F;GH ,**. ' 1 i

9mn³p&'¢\R¡d4:cF;5Cc

H =mD|w M'"rsF CDIJItquM-ῌ,vD)EwFM;DF ,M +  GPS µHqB

GPS ῏῍ῑῌ῎ῐ ,e0 %Z$#)¶ d47fG , 3sFUVHx

r + S%Qd4U.)·  Z$#)¸!

F] qyz{|}~)IMD^S%sS%t)S ¢]()B

D JK4>LD@]M 0 ;^aR)·F +. Bu) + B: )aM]  !"Z$#! rD d4U.R ¹d4:u#$B  TAK .>M>0 )NO D C  +* km ºDM£ B v-»¼wuM

 E  Md4:P)DHG-M Fig. - G/ )dkD· U.yDµHqB,**, 'e,**/ ' - d4:GM %-;k<l) Table - Pu c ¹B Ddk¹lU¹mº¹ n¹op¹1q¹»U¹rs¹¼1

368

E 

a

 1 B ,+ῌ,, $89 :d-+efgh
G%

EbC 6c,

DH!*+ 1

*Q;9 <R1<i=j>k/?@0H+/ ,,,** m ?.
A-+  ,i=j()B$P`[+-ῌ- 
,**- ! / B?l KWS <RCQ M+Z-

Fig. /

mnDo#- - E pF NRH+GH

 1+XJ

25

qI-+0r KLMs tu$NH!* *vwxO
yz{[+ ,**. ! / B|D - E 1+
;9#-` mnDPLM"RH} $~JJ89M(R EE1


R`H+ /NRH

mnD/PL$/S45[+ ,**. ! 0 B|<

Q
7++ B( M,  M-++ B +. $ TU$ . @#(

V&E +&WXCQYZ + [/0H+ YZ  !UmnDL"
Fig. .. Horizontal displacement vectors detected byrepeating GPS measurements, from April toJuly, ,**..

 .

GPS Y 1$. +<61ª1
 ,**. ! .Z1 B 1EF()2^_1j *Q $X/ KWS ATU,VWC

M, 

01 mm, M-  +- mm [  ,H?l M, //r

/ ,HYZ  h{M\/<R}HH+
YZ

Fig. 0+45LM$ ,**. ! + B?l - mnD

#- 0R]E -+ $6"^ A6;(()$
DH+ E_ "+C $&o#- - `a M,  0/ r ,**. !

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

./0*1

2 3 . !56 7*!

4$/  89:;4-+,

0 B|<R ,**/ ! - BD

,* mm PL[ [ +, BD`aPLM[ / P&b *$JJ89M[+ &E  +,BD5$ ¡cn

+EPLM ¢¢ d*£¤/[+,/#¥0H+ q

M+  M-0 M , f¦6eoM[+/?[+, BD

M + . +*mm, M- . 1 mm PL[  ,§* M+Z

 < 
,**, !.=>?" / @#. A,**. ! . B ,0
ῌ,2 $C D

EFG% 3HIJJKLM/NO  

 40H <  $<$/ @#&E' 0 @# A,**. ! 1 B ,2ῌ-* $C 6

PHD 40H, <  1EF(- 1EF(¨<R¦XnD gh0H!*+

 M, 1©Eªh$!*+, 1EF(¨i=j +  «3
riO U¬ORH+
&E =>?&121+ ­®9;

89:;/NRH (Fig.

 ,¡cn.?¯ °H!7R} &E=.) 1+<R S* KWS ATU,VW 1>&<¢¢±²³'-+  ´ µ:-. 2 kmC X/$!#$  01G%

9

)-+

*Q



Y 1$. (G-ZG2)  /Z+* mm 23[+/\] ,,,** m ?. AY 1$. G+ G. 

, ^_45. E, C, G, ONI, TAKC

,HR.¶·=¸_ A+i=j­µ

12623 0/.0H7/[+ ,`

¬O+


`q3 ,**. !<6E1 7)+1+*
Table -.

$%G+ ,**. L/;J¼¤ Lªqª«¬­369

Horizontal displacement data of GPS sites in Asama volcano, ,**,ῌ,**.. Reference point is G/.

7 - GPS 5 6 |<"( h- ,**,4,**.  ,**,  1  8¸¹ N9º:l \] »º G/.

  (+)

  ¶·

mn"!op1YR qrstuvw# H
Ixyzu{|} /$ ~Z% .+*+* Pa 6,**.  1  ,+ῌ,,  EC ! " #  ,**,  + $% ,**/  -  &l!'ST (& ')T \]uF xu Fu{u ETAK  & ' 1 mmῌyr  ()!

s 6\|}%+J/*%+ ,GPS -

)*

\]

k MaGCAP-V ,+(,),**.  . . (. / ,0ῌ,2) $% 1 . (1 / ,2ῌ ,**/- )T \] fg L HIJK-*) /0 '1%2   3 *4 , ,,,** m ,/ -/* m-

+* mm
(-)

! " ,GPS 5 6-,**.  0 7/

89!:6 +, ;< :6 ,=>-$- +.

+*- m- |<  U+Y PPL HI/J

K . / +./ km

, ,** m$- ,**+*- m- 1" Fig. 1  + h ,01 -?+% - @ ABCDEF U+o3YOB S , @ I$%de+ h ,¡1 - ¢6 < , @ HI hG.ῌ+ ῑῒῌ῎῎ῑῒ῍῏ΐῐ3¢ £¤ ? L ,, ,,,** m-

GPS 5

 A PPL ,,2¥-6,**.  . 41 %+

(Fig. .)  HI/JK LMN 1

HI uHI u B ¦§?O PPL3$1N+QR<OB S1T U?+<¨©  ªqª«¬­ 3® u B

? VW , @ IX6 Mogi (+3/2) Y!G+/Z [ \]^ , DEF-_`abcY

O 5±'S1 ²-*c E  ! udefg

hijkF lB

hijkF!

.¯°?

<4!1

o6!!³S´c%+?!µb+ 6$6Xµ(¶µ·¦µS¸µ)¹µ*µº¶µ»+µ¼

370Fig. /. Time series of slope distances by EDM withweather elements correction. Anomalous gaps
in November, ,**. at M, and M- were due tothe hitting of the ballistic ejecta to the reﬂectors
on the November +. eruption.

 /+ POP \"#IPQ (KWSM+, ,, -) c ,**-C,**/ + P-v
>!m*"">#+ M, M-  ++ 3 +. 4 ¡$%¢
%£¤¥¦§'¨*" Pl &'© H701 mm '7+- mmJ !"+Fig. 0. Slope distance change by EDM from January, ,**. to March, ,**/. Artiﬁcal gaps inNovember were eliminated. Bold curve represents variation with smoothing processing.

 0+ POP \"c ,**. C,**/  - 3+ ª«Pl  ¬Q­
6 ®¯\";°@+ ,**.  0 3±
0 +, 3±,>²³tu´*' M, PQ>>!"+<\"]^_> E7C YQ` +* mm DE-

ab E7TAK, C7TAK YQ`c%*E 



@"'- mm dA'&V efgh>!"+&U i j;0klm*-<=0no  B  !"#$%&%'()m*"

*"+ ,- E %

-ab .C+2 mm&" OPrs2*S,

V 

5tuv"2'>6&01

 B ./

&01-2' 1 3 ,+ῌ,, 4

56- E7C #89:;<=   B >!1-2'?@"+ . 3ABC1 3AB E7C #DE +/ mm F
G HE 

 +* mm, C I / mmJ >!1-> 89:; +* mm   -  ,!-"+pOP 5 KWS ql
p



-+
<=_w=N xyl-z{|*}(Okada, +33,)

U2&1- .~

&w>!"2'0 0"\  =

E7C #&89:;K LM4N

OP;>&%+

 2PQ,- RAv%<=v" !-V B RST1UV; K W

OPX +,***C,,/** m '%"2

GX%YQZ1-0Z'()*"+  B [

'()"' &l-

>

-

\"s m01-+l12K! ,**. *HuE.Ik«HIj-jº»¼

371

km, Fig. +4 ,**. * 3F++ G$+!,H-.

I$/=JE0&$ *.+ m radian "#CDK!J  )LE9 ,**.4 GPS 12K!
 1 GMNO2P B Q34R F S5K!
CD) . m radian T6<!

!CDU7830VW$<WX
K!>

YZ9[ V AW

\:;]#^_ 

>J 

,H-.I$/=JCD+!K`O2Pa
bcde fg8< ;h! =hiO2PB Q34Rj-jk>g8  $?

 ,H-.I$/=#lm$nPQ0@<o;p A$<qW!
.ῌ, 

EB'CVr EsTAK 5D$ 1 mmῌyr "#ESFGt T! 

(Fig. -)5D$T!

HuE'CIJIQ3v

Kwxy O2P B $% EsTAK Lz/<MN

 O0 (,**.){P9 (,**.) $%>J|QK!J }RESK

M~TM +F- km "#$0UTJ g8   V 2F27
!O2P C  $#

>

W (+302) $%!i SXYIE>}RE w(Z [K!J < <D\
J12E&I] wE&IC), km ^_E` 



ma$:XK!JIj-jV&TJ 
g8  V  (+33*) $% +3-/῍+3-3
Fig. 1. Observed and calculated horizontal displacements. Two pressure sources were evaluated byﬁnding the best ﬁtting location.

x 1 ,**. * GPS $%c_yz
12K! , Q3v ¹ Q3v'] {|¹ c_} }|¹Q3vK!c_*u$bJE&h=>cd'e
.* mm f

K! E&IC) , km ,g#hf i!J 

mS ,* jk .I,2le¡hmS> ,**. *.I¢# mS¢#$$£i < wE&I
CmnC¤+3-/῍+3-3 *$T!f¢

o@$TJ g8 

  





  !"! #.ῌ-  GPS ¥&p.I¢¦§¨kQ3v*+,q!>

E&I$?#©rª

$%&' ( )*+,-.I«<=W!J  .Ik«Q3v./01234 $567 )89 ,**-4 *+,¬s#  7 :;$%<=>

 e7®*+,$% ῌ ?

!@

"#>
A B$%CD F  )E&''() -<&M, ¨­

- Dªt¯°

±c2$3v²³a2´2# µu

.Ik GPS ©rª+2´v¶<·;$.Ik«E&I:Uw# 0 Gb¸]\·]¸·^¹·_·`a·Gb·º¸·»c·¼G

372'W !L[\eB^gW># [\eB !] * m, /**&,,*** m +** m ( ,,***&,,-/* m hG!]i  /* m (,. )39# 

XRW 9  G

H j*kL+l,m- 4[\.
B1n  +/0 o1` RAWp2
p# 56q3KL # 7>4rsOt` 5j678 9 uR /# 5j67
8SvwxsOt bc:yGlz #{ |}/* m ~w;

<# G

.Y+*+* Pa, G

=4rr*.,/ bc-?@S)>,,/** kg ῌ m- # XR

ANSYS  ANSYS ver. 1.*

# sOtA

 +* B9#
.CKLf;&^  M, ,* mm
Fig. 2. Relationship between calculated slope distance (M+, M,, and M-) and amount of increase in volume versus height of pressuresource.

´ 2# [\eB f;&^ (M+, M,, M-) [\^ µ¶# KGbc%$ M, f;&^ ,* mm L
 !L M+  M, ^ ^ .
n# [\eB!] +,*** m M E
L 456 (M+ : +* mm, M, : ,* m,
M- : 1 mm) GHWI #9 >1 'WU  `B1[\eD n 7 M+  M- f;&^XR# Fig. 2  [\eB h!]i

q3B1 M+  M- f;&^ U 
9# 456 (M++* mm, M,,* mm, M-1
=

mm)



'WeBEL 4

F9> Z"1 [56 9\eB!] +,*** m M EL 456
GHWI # U .J. !] +*** m[\9_ ,,***Y+* m L#-

 (Fig. 0) +,M, 1  - mm ῌ




!

"# . $%&1 $%

-

[\
TA

S,T A

|

}W# ?S,T A eB!] ,,,** m 93M, '()*+,- (G.) ./01 GPS 23

bc:!] ,,-/* m 9> Z" }C456  78  0 mm



S,T A93 8 : ;<=.9 KWS

+, :3.K [\Z"  #  
;4B1

GHW[\

 (Fig. 1)# >>? . $%&!] +,***&,,,** m  93 U .

/ GPS 234@AB1 0 mm

e _ ,,***Y+*- m- .K _ /*Y+*-
1 $%

3K_ XRLS,[\ 3. M+ M-  CD  0 &1 $% , E>

> MbI 3 N% bc: ?A}

F01#GH GPS 47ICJK

L : ;4 1 MN.L1
# 7> GPS 4O,Pm- L#Q

RAB1S,TA U 0&1  , E> > +* Cbc:e? +** mhO+P ,**/i  , +**Y+*- m- .Qn bcRST+l ? l ¡¢£Ur9# >¤¥ V

U VW +, X /*Y+*- m- ¦Wn 5j678

9Z"1# >1[\XR /# bc: Q?  0 +* 

S,T A  78 !] ,,,** m ?^L?

1ªWL]B9 ,,-1/ m hO+P ,**/i 

_"93 >`# $aL # Xr«¬~,Py­®¯°YZ± #7> Gbc%$dLeB \ `

XR KWS ?4B1f;&^3l§¨,©)756 QI M+&- 8.

bcN²$

K 8  *.*1 mm [³L.9# b

}¼*:;dV ,**. <=>?´= ABACDE

 

m

,**

373

+* m ABASCDV.2--

 !"#$ %&'(

YZ[\ B]3 / 1  ,+ῌ,, @>c - )'!"* +,-.#/01.

 , opS5TUV23 z{|4}~ab(,**/b) F ?~ OP

23

Z[\ C :;?l c/:;O?
/ 

l +,*** m X Xf`9Sf$*4567.289/:; ,**. <}~*ABACDESV3 =>?@ABACDE8FGH =>dV2Z[\ B  ~:;dVABAC

?= ABACDEIJKLMN (Fig. 3)3

D:;V/#3 .:. z{|4}~a=>O P Q

R5ABASTU

VABAWX$ YZ[\ C] S^_`3b (,**/b) F Z[\ B  a+*  ,2   /  }~S .3 X

b  c^_d5ed #:f2S g92?l~+?l:;Z[\ B (,**.) h ij (,**.) F$ klm +:fzS¡¢.3 /V:;z{n- km op9qrstuvwABAWX$^|4}~ab (,**/b)  =>?P8 _SxyV3 X2 z{|4}~ab (,**/

E£ABACD^_¤¥¦.3b) F /m +n+./ km ~S^

X2§ij (+31/)  +31- <? - <:; ¨_`/+;:V3©#~ª«;V#SOz= ? .  n1 =>Oz +./ km 

¬5#}~*S­f2/®.3 ¯

Fig. 3. A model of magma supply system of Asama volcano during the ,**. eruption series estimated from GPS
and EDM data.

° 33 ,**. <=>?@ABACDE±²IJK3 ,**. < .n1 :³=>PQ ABAW
X$ (Source C) :; Oz +./ km m­ABAWX$ (Source B)  ,** +*- m- AB
ASCDV23 c´ ,**. < 0 8´ Source B :;O?lm ,,,** m ABAµ¶·¸(Source A) ABASCDV ,**. < +, X #¹+ /* +*- m- º»S­f23

374

E¦¯»E°±²n³´µ¼

B   (+31/)  
,**. - .m1 Y30( PMN&'

Aa %~a ,,,** m )!

(}` ` ! "#"$

123cF +.b+* m- )&'( (! 0 Y:U:%&'()*+,-.

;/0+1!

C +1

-

/'(,-.1QR}` `B 2

Ba Q3!@ +./ km ~a[N 1

3"#"4567 8,90Yb)123cF ,**b+*- m- ,&'(* +! &.:;45"#"45<= >%?@ABCD*B 123c - c , ! 1 Y ,+ῌ,, 4No

3C()EF (+331) G*HIJK+1! 

vSw0+1! 1%QR12:;! 5Q

L <"#"45! MN!+1"<U ,**. - 0 YZ+15Qde +, YZ)f<#45$O! P1QR%)SB(,&'( u(}`123

,-. ,+1TO!MN

cF?h! 'B ! !+1"#"45<U(&'(
,V%& +T)W)!

C ,"<#"#"45<*+! PB- GPS gk1(>o*h;! fi1BR}``

Ca $Oj%,-.

j1(0! K3! kA)l*/J+X67 8,1*,**. - 0 YZ+1QR%.E ,,,** m [Aa! 1 Y"#"\]^_"#"45 /N `0) +.b+* m 123c,*N! 3 Y + 45--

fRB

C +145*6+! &}`BYMN@ /*b+*-m m,,***b+* m ,k2%1(--0m= ,MN! nHI)Q3QQ
R"#"45<M1+(o! 10

|! x3EXY*0p qr)ug! "Q'( Pd +, Y5Q$67)! 5Q$#"pNs}`r_ EtY)' 

MN 58eN9* 1%! "#"45M,  *

12:;f<(A=><6(%

! K3cE0 `(<0a )! "#"45<K3& u)u, g?h)@ /*b+*- m- 123c &'( d! "#"45<uv,(! 5Q$A:;

B! wx yz'%{*/A MNB+'(,(CB! PBD*i,%.E +,*** m :E&N!

HIVC

0V|} &P123cFEj ,,***b+*- m- ,k2%1(lN! "#"45,5Q$M58GHI)ΐ&@ /*b+*- m-m,,***b+*- m- "#" ! QR%nHI0! ~*`,ῒ( (Q 8 0`

"#"\]^_J2(,&'B $O ,**. - . Y0, 1 Y0 GPS( R= GMT

_¡ (Wessel

eN90MN&'( ! =>n/Ko P

and Smith, +33/) ( !¢GHIQ3

3lp'(+LM)& (<0)! 1 YQ0! GPS 0(£¤q" ¥,+ῌ,, 4No3)"#"qrDu! (¦i¡§¨ stO)u%

! =>n/Ko)P')u* +! MN
QR"#"\]^_ `Aa =>n/ vSw0+1 0 YZ+1)&'(,&')u)!
B =>n/Ti% 0 Y:Up'(,-.

(©x! yz©x k)&f~GEFª«+1¬­kn®¯ E)'( PEF°RC(N±z*²i,,%! (*i³+R,*´_.( (! !fGd, VW)&¡¢Wµ£®{=slt*
0ῌ ῎ ῍ ῏( ¶·¤ 

K3x3EXY* GPS 0yzvSw0
Z{[! ,*** -MN0n/( 0Z
MN ,**. -5QUd|617

8

,1

(
GPS 0+1! QRA\, ]^_1ῐ ῕ ῔ ῑ¥¦§¸¨©ª«¦ (,**.) ,**. -Q35
Q¬ / 4nQG¹ ,**. -Y­º¹®®¡! ,*/.

 " ,**.
 (+302)  
 + +ῌ./.
   (,**.) ,***     !" ## 21 ,2ῌ-..
$%&'()*+,-./0123 4 (,**,) !
56"#789:;<!=>? GPS @$ABC?DEF  .1 03/ῌ032.
%GH1IGJK&'($%&L)*M
. (,**-) +L,.-) !!.NOP
QR /&# ,**- ST0#UV -/.
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