ῒΐ  // (,*+*)/-ῌ0. +῕ ῔ ,**2

2



,,



m·¸<=¹º>»%¼ ½?e@<,**3

2 E 2 F ,*+*

+ E +2 F

Products of the August ,,, ,**2 eruption of Shinmoedake Volcano,
Kirishima Volcanic Group, Japan῍,
Nobuo GESHI῍, Shinji TAKARADA῍, Masaaki TSUTSUI῍Takehiko MORI῍ and Tetsuo KOBAYASHI῍῍῍A phreatic eruption occurred on August ,,, ,**2 from Shinmoedake Volcano, one of the members of
Kirishima volcanic group, Kyushu, southwestern Japan. Some explosive craters and eruption ﬁssures aligning in
E-W direction for 2** meters were formed inside the summit crater and the western ﬂank of Shinmoedake
Volcano. These craters produced clay-rich tephra, consisting of non-juvenile lithic fragments with various degreeof hydrothermal alteration. Ballistic blocks distribute in an area within 2** meters from the main crater. The
total volume of the tephra produced this eruption is evaluated as ,+*2 kg. Distribution of the tephra indicatesthat the main source of the tephra is S-+1 crater, which is the largest crater located at the center of the crater chain.
More than 1*ῌ of the tephra deposit inside the area within + km from the craters, suggesting the low height of theeruption cloud. Absence of the juvenile materials suggests that this eruption was phreatic caused by a rapid
release of steam from the hydrothermal system beneath Shinmoedake Volcano.
Key words : phreatic eruption, tephra, eruptive volume, Shinmoedake, Kirishima Volcano

G +330+ῌ ῐ ῎ ῑ ῏OP !Q,JRSKTU ,**2

2 E ,, 

21HIJ +3/3

VKWXYZ[0S+33+

KLMN\TG+33, ; ]^JK _`TKabc dLOPQe"f +3/3  /cJ gK +1+0῍+1+1

ijJKTkWlm1 KnUopq11

U MNVKbcrsrMNVK rsrKtu

hvKL wx!UiyzL{"|}L~J0[U|}1uW#c[0S e +33+ $%hRSW LKJY_`TKa&'b[ Z1iMNVKL

cT(Jb[ dJ) 2** m J1Y*+

|SuU ,L_`L{"-ShS.LKaVW/1 LKU

/hRSq

2 E ,, L + h01W /1KazL

21 ¡1M¢L{£J2 0¤S MNV

3bcUMNV¥¦uS{iV{"W§¨[K U©4Jeª5hURSW «67JZS

0S LKU¬8i9L­2i0KL©hRY zLZU¬8i®:¯°2i0¤S MNVK u±cS _`LmJ

0uW²0

U1M¢W³[0SuW#c[´Y \T 
 -*/῍2/01 

Geological Survey of Japan, AIST, AIST No.1, +῍+῍
+ Higashi, Tsukuba, Ibaraki -*/῍2/01, Japan.
 --+῍20-2 /012" 34,῍,1,῍56789:;<=>?@=AB  CDDIA Consultant Co., Ltd., Sabo and Disaster Prevention Division, ,῍,1,῍- Yoshino-cho, Kita-ku, Saitama--+῍20-2, Japan.

q[ LKLZ

µSuU _`KTL{"LµJ¶;SL 23*῍**0/!"#$ +῍,+῍-/!%&%&'(&)*+,)&-.
Earth and Environmental Science, Graduate Schoolof Science and Engineering, Kagoshima University, +῍,+῍-/ Korimoto, Kagoshima city, Kagoshima 23*῍**0/, Japan.
Corresponding author : Nobuo Geshi
e-mail : geshi-nob@aist.go.jp

*+,

54

-./ 01 2 3 45

Fig. +. Generallized map of Kirishima Volcano. Dot-line shows the approximately outline of the volcanic
ediﬁce of Kirishima Volcano. Representative craters are also shown. Dotted areas show the areas ofthe volcanic ediﬁces of Shinmoedake and Ohachi volcanoes. Location of the eruption ﬁssure of the,**2 eruption and the approximately distribution of the ash-fall area are shown.

678 9!" :;< !=>?@+33. ; AB C0 +3/1 7D  !"EF!"GHIJKLM

NO #$=P74QFR!"M  !"#$ ,**2  !% &'(\]^_`7Dak 3 dlk

)!ST U&VWX7DYF!"KZ[ !bc 2 d*!" efgh"UMi j9

J!m ,+* km no]pqpgrU&stguvwvxyzJ{|}~  !c

0B 4 ,**+ ; AB C0 +3/1  !",**3  , d"!m !  =

&

Fz!

m~ j  !=J
Fz!m& R= #$i!I )IJ{ +102 "
#$KUIJ{ 0B+33/ ; 0B

4 +33+ ; 0 9 ,**/#$ $ +.,+ m  !",  

 !"%!"pxlI

h"UFR!" "b 2** m¡ ¢£ +2* m ¤ !m &'#$"!m¥ ¦§¨ ,* km-* km (© "ῌª« Z[ (Fig. +) #$¬)­)®*+,¯!"N°±7²³´!"

7{

M (Fig. +) 0B +33/ ; 0B 4 +33+ ; º"ka BP) =i»{-µ¶·$¸¹4@g (+0.1 cal#$¼".½/l"#4 ,**2,,  ($

2

56.7 %-89:) & ; <='( /* km2+,?@7 0+A, +33+ #4-B  2

  

55

#$)% >"* 3,,  ,+   ! " -***

CDE5.F/G0 1H-IJKLM! 234m )JN!'((  +++/ mῌs NO/ .7 ,P5 (+*.. cal ka BP) P5 (/.0 cal ka BP) OQ

: 6T U7P5 (8 +1+0+1+1

 9V5

:W';<.7(=> .>+?@ WX%

0Y6 +322 67 *Z.7 [V\7#A; 6B7. -/ C]^_%

4 &!%-89@ 1 QD`/

#$% ,**2  ! 2E

2FG U7P5 JT !a,HIJK
9V2+Q :) !@O

SeP Qe

,. 

bN :

!6R.7

36-S #4,, !<W2WcX: dL.7 MN%

(fR2+, g #4.7 ShiTj

-klO/?@7 0+A, +33+ -&' (! ,**2) !*+,-./67 mUVW 8 FX ! nY (,**,)

  +* 

3(Mori et al., ,**1)

oN! @ +* pqῌ (U7 +1+0+1+1

 U7rS  !#4N+,  COMPUSSZs7

7+,t1 NOQ [ u\v SQ
P5IJ2w. x]wy^

]J2 

_ gN`2 U7 /+ [Vb7#. 
,,  ; Wc! #4:W '2

4 z7.-&; 1<a; ?@7;a.7#4(={b6< .>+ [( 2** m gWc de|f }~g9U7 h\v ai5 (Figs. , and -A) jk >Wl

9 ?@7 +2,,mn N!

AG0-I  TjQ rM (J s

op! %qC]^_% p*



 

.ῌ+

]tl+,>N1H-u!v#4:W '( !  eP >t+7 AG0-MN%NO/S -1 W (S-+1) ;  (Figs. , and -B) S-+1  #4! +11++11,

W!#4:WxJ;a `5y{b 6<Bw 92

?@7 0+A, +33+  z <W2+, 6 W 1H![( 3* m, '{ -**|.7 6 !}N26B7. m ~ +*-* m NO S-+1

 0 ,**/ +3/3

@ %`2+, -.N9 W wy -.

E /** m!

,#4(={bNMN%2 [(5W;  3 j+3/3 W.7 , km )c !1 

2w.  ¡c u,\v  IJ2 ,u 6(!

20* pqFG+, %q +3/3 +33+Wx !

< T5%t9eN % dv !%Tj-2+, ($*a! S-+1dL! XXAG0-W;

Nt1-
S-+1{ 2* m+, (S-+. ; Figs. , and -C) S-+. !wy|;N¢!
 .* m ~! +* m )6F% s!#4:W[< %.7%  (

GNH-./ S-+. !wyO,!XX£= ¤ ¥ +33, #4:Wc(={5¦§¨q©2xN.6gª«p¬­>f ;fC2+, S-+.

+3/3

Wc

! 

).7?@

%®9V2+, %q ,**/7+, S-+* %q ,**/
 S-+1- ,**2 

#4JN! ,**212  

; T! )[ +** mT wy¯5! ¢@ m .7 +* m ?@ WO,!°<W2+, (S-+0) S2+3 ±².7U!

+. X S-+0

dLN!($*a!a8-7 °,,  ! -+,  !3

.7!w~³($(-./6C´2 ,,  +0  -. a±².7R/-UP

+, °c< !2µ2µ $¶·«¬f2 -/* alfR2 C]^_%#$% ,**2 d¸ #4.7{[  +* km A,¹cN Q Iº3 6 Ph,2F #4:!a,» S+,s¼!½+,-, #4

2+,
S-+1[ -** m#4:W'<!%

A;  (S-+/ ; Figs. , and -D) %A G0*  ++.    







,+

+*

/



56



 ῒ

Fig. ,. Distribution of the new craters (S-+.+2) formed at the August ,,, ,**2 eruption. Base map isthe + : /,*** Geographic Map of “Kirishima-yama” published by Geographical Survey Institute.

῎ +** m ῎ ,** m   !"#$%&'()*+῍,-./&012345&67829:;-!"<=4>8 ?@ABCDE9F=GHI&= JKLMBNO3FPQR5ST 9UV

WX"D!(829  !"<-YZ&ῐ[=\]8^V_MK8`*+῍,=a`+2bc *+῍def

29  ghi 0j& S-+/ -YZ&klmn-!(o&p`12 +, m qr-setu=vwx+  F

y=z{82bc S-+/ -!"|-}~&E9!(yb 345F*+῍de,-./&Ej5Fk-D='(x+`D829 .ῌ, ῎ῑῌ῏ῐ῍ῒ
S-+1 -&` *+῍&&Ii FPF
1`&*+῍d

JKLMB-3G HIF!"H=G

e=}~x+` (S-+2 ; Figs. , and -E) -*+῍de+ !"<-YZ&ῑ-ῐ[=\]829  `

 +3/3  , !d}~x+`deΐ- 1*2* m*+῍de-YZG&2 *+῍deG& ¡&I829  *+῍de ¢k`Gx+`!(y=z{829  !(y*+῍dde-£ ¤¥῎ +-1* m G -¤e-j¦ !"H=HIFJKLMB-3§¨¥῎ +,/* m #©\§&2I82bc ª-W«&¬;F129 ­®῎ -/* m   ` *+῍de-¯°3Fb ¢deT& ¢de£&F*+῍deG&4±i ²ῌF*+῍=³´

se*+῍=}~x+ ª-µ3GkHIF!"H

G+  *+῍de¶7·῎ +* m  ¸¹ΐi ³=ºG+ ´-JKLMBG»~x+  ¼῏FJKLMB½¸¹ΐ829(Fig. ,) *+῍-se·!(y- ,**2  2  ,, 

57

Fig. -. A : Northern view of the new craters and fumaroles inside the Shinmoedake summit crater. Notethe E-W alignment of the craters from S-+/ to S-+2. B : The northern view of S-+1 crater showing
E-W elongated outline. C : S-+. crater surrounded by a vertical crater wall. D : Western view of the
new fumaroles in S-+/ area. E : S-+2 crater chain on the western slope of Shinmoedake. F : Fissure at
the lowest part of S-+2 crater chain. The width of the ﬁssure is about ,./ m.

/   !"#$%&'()*+ , km

/ῌ+  

,-./$01234' 0156789:$;,**2  <=>$?@A'< !B

S-+1 + 1** m

CDEFG !"#$HI JK2 (Fig. .) 

+ .* mm LM< S-+1 + , km C+ / mm

 S-+1 FGCNOEPJK23Q NL

LMR ! S-+1 + -.- km C+ , mm C;S S-

DE S-+1  BC+ , m C;' (Figs. . and /A)+1  1 km T:UVWC DE + mm TX

YZ[\ (S-+2) B !Z]., (S-+/)

C;S^_CNLDE -* .* cm C;' `a$bcdeC + -* km .

58

 

Fig. .. Distribution of the tephra produced by the ,**2 eruption in distal (A) and proximal (B) areas.
Unit of isopach is mm. Small solid squares show the observation points of the tephra thickness.
Numbers show the thickness of the deposit at each point. Symbols “ + ” mean that the existence oftephra layer less than + mm. Symbols “( + )” means the existence of the trace tephra deposit. Broken
line shows the rim of the summit crater of Shinmoedake.

ῌ,**2  2  ,,  59

Fig. /. A : Tephra deposit at the eastern rim of the S-+1 crater. B : Section of the ,**2 tephra deposit at
the /O point in Figure 0. C : Section of the ,**2 tephra deposit at the .Q point in Figure 0. D : A
ballistic block landed at about +0* m southwest of the S-+1 crater.

  !"#$%&'()*$%& ,**2 <=> mm ?@)AB

CB

DEFGH@G I)JKLMNG: OPQῑ8[;\FB]^_`+,-./012ῐ3456789:;
/ῌ- ῎῍RSTKUVGB 4WXῐ3ῐYZ
abcde>fgh-ijk; (Figs, / and 0)
Flm S-+1 cdnoK῎ +/* m ῏ / J )B/ῌ, ῏ῌRSTKUVGBΐ012ῐ38pqr
stuvw C_; xK S-+1

RZyz{

῍ RSTKB Fld; -* cm 8
l;5p>r;

<B5kq - fgh-K#7k \dfgh-B7|}~K`H῎ + km K_; (Fig. 0) ῐ ZWXwcd \df

Rcd῏;K

gh-B RSTBdKe>0fgh-K#7

HῐBKG ῐ . mm 8l;k; _; 40fgh-ῐ3FB

BῒdHw;:]^_; Unit A Btu

Rcd + km ?K@GHw;

S-+1 cd῎ 1** m ῏7|}~K_;vwῐ ΐcdQ ¡¢£¤¥¦§¨©8ª« Rno¬K¥­;®5ῐB῎ / mm  ῐ 0

­

12

Cῐ38pqrs S-+1 cd῎ , km ῏; S-+. n¬6 Fig. 0 ¶ */J ) B Unit A B

5·«¸SB®5ῐB῎ , mm  }K +dK@¹6./¤<F ¹6ºΐ8rs¦,-012ῐ3cdWX; 5·»no S-+1 c

ῐQ , <K#7k; Unit B B¼a./cdQd῎ -.- km ¦½*B + mm ?@ῐ3cdQ +,- 012ῐ38ῑrs Unit C B®¯8pῑKrs:°±KZZ²³a8´µ()*+,-./ 01

60

Fig. 0.

Representative columnar sections of the ,**2 tephra.

23  4

"

Thickness of each bed is shown in mm.

5678/* cm $9:;< =$9>%&?&@ABC$3D E F!GHIJIK  $9LM"C#N  OPQRS Unit C %3< 8%&

3&[3\ ]^ Qde)4f ghij  k!l!
-qrst!i S-+1 u.4viqrfw
(Fig. 1)  S-+1

  k

! >!GHIJIKx


!

{

34~3D m __ %&(Fig. -A)

U y/ !  S-+/

XYX3$Z
  $9(*f3m no3+3$3\ 56,pzU y/ ! S-+/ |}TU VW ! _'`abU($_(c$y/ ! !01

$93 S-+1

2!U

(Fig. 2B)/ῌ/ ῎ῑΐ῏
S-+1 

3435 , km 6!U78u.4U ,**2 9T& #:;\;

~!<3 - ^ 

: =U > + mm < k!l!%?3|K&?XYX3$Z ab

 !  k!l!|u<3)

UC$ c

@7A h 3 ;< |2B

 !

!l!Uk

{ e)

!

±J4j T

#$  %&'@AB$ F

5 2** m M¼3(Fig. 2) S-+1 ½N3 > + m OW$9  ¤C¥CD¦4 v>$ © ª

-#  H&$ :¯X!  XU°Iª
²&cA3¯X!  XUZ³U³´ZµK¶· ¸/ῌ. ῒῐ῍ῌ

2$9 S-+1 %»"&¡C$C$ ?¢p £w7A?&¤C¥CD¦\<§14q¨#E` ;\«¬3\ ­®GUp

(Fig. 3)c  ¹ VW ! Lºx()*'+, ,**2

Fig. 1.

2 - ,, . /61

A, B and C : distribution of Unit A, B and C. Unit of isopach is mm.

01 (Fig. +*) 2/ 34 567 /* mm "8 #0ῌ ΐῐ῔῍ῑῒ

/ 34 ,**29:;1 :< =>?@A1B C@D9 /
34?@$@3GHLM NOP ,**+ <QRSXY?@ (x) <ZGH=>?@A1B XY (y)[ S-+1  ! + km " #$ %&'+,*E<FAGH <IJ
 +, 

 0*ῌ <K1H

/7C@;TUHV9W;TUH

\L 56 , mm "] # 34^_8$`

a9bS[c yaxb $de; XY?@ Ifg9@3

 - km "h <X];12/ iIJ

GHV<jBi 9kl;1 =>?@A1B]m@n0H+*ῌ "XY op9jBqrde$SHjs / fg<f3;T@3;1 (Fig. +*)  , km " #$1ῌ ῎

/ C@956$:;11t '+,*Eud,**2

jvwx*ud- yz$:;1C@/(+./*, +.3*, +21* kg/m-){|

} +0** kgῌm- 9UT

56=>?@A1B C@D<l;1

 ,**2 ,* ῏ ,* m@n0H

V }'+, +3/3

 20*  ; ~ +3/3

jB $KH d $;1~ K
HU~GH D* +33/+* -  ,*,*** m ; OP +330 , +330-

62

 

Fig. 2. A : distribution of the representative ballistic blocks. The /*-mm isopach shows the approximate
area in which the thick tephra cover prevents the identiﬁcation of the ballistic fragments. B : thelanding direction of the ballistics inferred from the sag structures.

,**2  2  ,,  Fig. 3. Thin section of the pyroclastic grains of the ,***
tephra. Arrows show representative grains which
was su#ered from hydrothermally-alteration.

 ++ 


-.0

 

 ;  ,**1 +330  -  /  +331
%

 +,

+,

63

Fig. +*. Relation between area (m,) and weight of eachisopack (kg/m,) for the ,**2 tephra. The weight of
the tephra per unit area was calculated by the
thickness and representative density (+0** kg/m-) of
the tephra. The total weight of the tephra wascalculated by the summation of the integration of theapproximation lines in each segment.

 ; ,***  -  -+ !"!#$

 ;  ,**+ &'()::;<9&=9 >=?@ AB ,* C8D
L5M#$% N91O!"!#$% 
OAY Z= [\N9

P< QRSTUV8O =W2X=]^_`.HI0` #a#$%.5M),**2  O >b6cd e3fI561

M 1?j9kk)h=*+,-./012&34567 #$% 89
EFGHI3JK>9h)=!kkOl

3V>92&.gN9 S-+1^)h 2** m i;

m"nop.#q5M2&O $=#$%%&0`61=1 kk'(O0nrn=8

.L5M2&34567 ]^_`HI&N#)k3*sMo+)h=9 22&OP<?t6 #auv.LwM2&34x5619 ,yz{.

e'8|>9#a)h#$8O!kkO}0`61=1.  ,~8%89 1?j9 #$%  N !" +* tῌ-..& h`M2&O!.'n;5 /08,y>9

!"!)h("5MO=)sM2&345619 P< 81s6H

34x5619 F

I0`M4 2** m 8?M9'(,= ^5O

35  36>97Oe38>99 +, m ]^_`HI& `3:;&>9 e'#a)h#$%345619

>^8O ,**2

.#a80`M2&
23.#aY0`619 M&  55L5619< Y !"!. ^ =n 8

230`92&.-&=s619&h`61

 i )h%.d¡5 ?%@AB¢)h e

9 (Miyabuchi et al., ,**2)

,¤8O =#a.|56192&.Ch`6h7 ©  +330 P< O#aª0`67 ©  +330 «h)z{8

.z{&h`9¬­®¯.u°5M2&.P< -&P< O  0*ῌ . ^BE + km i8±¤5M2&.FGN9 F8 Y£'!"!).#a8¥¦0`619§¨+.D=sM7.N9

 O +3/3  +33+ 8 

H²T`³` O´=9Y#$% .L567 µ. ^BE + km i8¶8±¤5619

P~Y2X=#$% .·I5L>9Y&2X= ^BE8¶>9±¤ µ(JO P¸?`9< G;.¹ 6)sM2&34x
5619 ºK»M GO¼0`61=1.

2ῌ ῎ ῍ ῏^,;G;.12&O GLK\½

,**2  2  ,,  O> !  "  64

 #$#%&'( )-./  2** m  #$ 0!"1
2 314 3* m-* m   (S-+1) 5 6(78'   9 )

<( #$=.
,**2  4 ,* CD556'(. 4FG9
2:HI. 4;  

31 S-+1

4>N S-+1#$4'( M@

#$ 2** m AOBC1 

4 0*ῌT* #$ + km TH#U9 1
 L$VWX :YZFG #$ + km TH9 1 L Q_ , mm T  U
*VW*H #$ - km Td 9 1 :Z[\ +*ῌ T HI.
4g`\.&F./#>0#$=8 'MhM=defg1#i2j>0ikl M mh?ij?=nfg1#3l
/#>0#$=8fg1#ikkl44*#$5F'(.lo,e ,**2 
0Xp2lqgm9i41rs.gm9 H
Ijt5inF.
῏῎

 %&oj 9]^ p u 4yz{9]v |wx6}D~ x6y

7%&

,|w

 M 4y ,|wx6}D~H '   |  8'

9^ z:P;' %&I8<i$j
 M = >;3 ?7.=&
7-@Go7.DC7j ";C'( T*7- ¦F§£1MFῌ ῑ ῐ ῍
4yz{9]v 9]v (,**2) ,­K B ,*  2  ,¯­K B
 ,*  2 
 >  °©    ±:  yO{¤ ¢² (³±!"L² ª²¤
¶L  ·Mz{9]v  ´N 9]v  µ!¸[(,**1) +330  B 2  ++ 7- +332  B
+*  ++ !"1º¶·  A¸»O #Q
R'6 12 ,+῍-/.
!* (+33/)   # ½;E pQR'
P6 03 +23῍,*3.

!*  (+33+)   -**+ ,  -0 +-/῍+.2.
!*  (,**+)   #$  #$ ++ #%&'!:*;+ (+322)  ,-.  ,/ >? 2- ,0῍.+.
@A0 (+33.) 12B3"1
 E78 +*- .13῍.21.
@A0JK<= >?!L (+33,)   +33+῍
3, ! 5DE9PF CA QRS +33, "G
,13῍,30.
@A0JK*I J<=K 4
  <MN  *[\  ]OL%  P&^`a b'( R)c; STU+ (+330)   XYef+
 .+ ,+/῍,,/.
9]^ (+3/3) 9],- 1+. _ 1*῍1-.
9]^ (,**/) a, Z- b - c /,.῍/-0.
Miyabuchi, Y., Ikebe, S. and Watanabe, K. (,**2) Geological constraints on the ,**-῍,**/ ash emissions from the
Nakadake crater lake, Aso Volcano, Japan. J. Volcanol.
Geotherm. Res., +12, +03῍+2-.
Mori, T., Hirabayashi, J., Kazahaya, K., Mori, T., Ohwada,
M.,Miyashita, M., Iino H. and Nakahori, Y. (,**1) A
compact ultraviolet spectrometer system (COMPUSS)
for monitoring volcanic SO, emmission : validation andpreliminary observation., Bull. Volcano. Japan, /,, +*/῍++,.
q5rLsrvL%wtx u(+330)  z  +33/  +* ῍+330  +   :#5>{  |EQR} (No. *1-***+1) ~!
%&QR +33/  +* z gm9!
!"f5 ,5%&QR QR6
 --῍-3.
9  (,**,) *F. - +E2QR bQR .+ ,,/῍,-0.
! (+3/1) /  + #$  -  #%&' /2p.
cALBT
K  , D  9    [  ¡¡¢ELU£;= >{¤ ¢¥x¨  d¤G  ¥¦©  9H   !§{¨ª«¤ ©ª;+c¬«­I{![L,  (,**+) J¬  ,*** 9®5 7  #%&QR6 /,
+01῍+13.
®¯6>° (+3/3)   +3/3  ,! #E78 0/ 1*-῍1*..
! 3´L  (,**/) ³µ 
%. ,**-  +, T99,5  ;¹
 ,  /* .1/῍.23.
µ!¸[  c  ²¤¶L   ¹  ¡L(+331) A¸»º» +330  -  4¼¼½  ., .,3῍.-+.
@Go 