ῒ῔  /,  (,**1)
 ,  +,+ῌ+,0 ΐ ῕    ,**0  +,  ,/  ,**1  -  +-  Geothermal Activity on the Flank of Sakurajima Volcano
Inferred from Infrared Thermal Observation
Akihiko YOKOO῍, Masato IGUCHI῍ and Kazuhiro ISHIHARA῍
In June ,**0, Showa crater on the southeastern ﬂank of Minamidake, Sakurajima volcano erupted after /2
years silence. Geothermal observation has been repeated / times since March ,**0, using an infrared thermalcamera. The results of the observation were compared with the previous data. Thermal anomaly areas
identiﬁed in ,**0 coincide with the previous results. Increasing temperatures of the ground surface wererecognized on the southeastern ﬂank of the volcano in particular around Showa crater and fumarolic zones, overthe data of +33,. In contrast, no signiﬁcant change in the temperature was observed on the southern ﬂank.
These results suggest that the geothermal activity on the southeastern ﬂank of the volcano became high prior tothe ,**0 eruption at Showa crater.
Key words : infrared thermal observation, Sakurajima volcano, Showa crater, geothermal activity+ῌ ῐ ῎ ῑ ῏+31, G +32* Io +33, U!X" t#u!


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!" +31.  +33, #$%&'()*+,v"#wR:xy#mT EG +33/H .Sz
 ,**0  , w{|L}$! ~ -.% /012'3456789#0:/01;<=*+>?@ABCD EF +31/ ; EG +311H IJK#"
.  LM

;N#<=OPQR:S.ATH U +31.V+32- U!WX#/$: %B 0  . # /2 ?.q:
UTH   "`+** mV+,*** m &"

X'qY!()$B /0I*XHGPS +*+#0T% +33/ Z,#m:-h%a:S.AY" 1/V+.1 MW Z[  !"

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Y"SB0?c,de`f -V+0 MW .g

hcB Table + ; EG +32* ; +320H.CD 1r +320   ; 2 +321 N#" +3-3V+3.+ #"<=O0%`B:S.cm?

!ij`,+  #+% LMlB +3.0 L ! *., km- k G ;N  0¡#¢£%a+32+ lYLm:H SS!" +3.2  1l¤:S."¥3!m:H IS! ,**0 #¦§ /lno#  " p%aqTH LM34¨©*+JK. ª«*+JK.l4¬

 " +310 U!" ;N#/$:< ;N ¢£#­a%®5H=O'! cT.cYrsTc E ¯23+ῌ+.+3 °±²6 +1,,ῌ+3³7r´8µ¶·¸9¹ ¶·º»¼9Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, +1,,ῌ+3,

Sakurajima Yokoyama-cho, Kagoshima 23+ῌ+.+3, Japan.
Corresponding author : Akihiko Yokooe-mail : yokoo@svo.dpri.kyoto-u.ac.jp

¯°±²^³´tµ^¶·¸

122Table +.

Estimated heat discharge rate Q [MW] from the anomaly areas

Fig. +. (a) Map of Sakurajima volcano with seven locations of the ,**0 thermal observation (solid circles). (b)Five thermal anomaly areas (,8C higher than the surface temperature at the normal area on Nov. ,**0) wererecognized on southeastern ﬂank of Minamidake (A-E).

, +M ,**0  -  ,3 /  ,,  1  +,  3  ,+  ++  ,  /  +3  ,+  !"#$ %pqOrstuvw+,-% fC+ G

X &Z[\]^_]N xydz[{|}r~! Or6r  {r `-kst K ,***M & Fig. +a '( 1 )*+,-+% . $ !kOr t

NEC /01 TH1+*,MV +,2 34567 ,389:;

 e,,8<=>?@ABTobs% CD +33,  E
K+33, 67+/89:; +*8M% G  STUVW 2L+. mm+,-% X &+YZZ[\]^_] `abA\]

hijG+3klmW+T£    n Ko ,L../ km ; Fig.

,**0  0 ¨©ª« Z¬­ ®! Q %¤,1-.+/2e!$ %cde - + X &fg

D8C¡ NOr7¢r\ tave 8C¡ FCG+ +. H IJ345 K67 ,/L-*89:; +2L,/8M NOPQR Q

$ % f$! *.31 K +31/M N$! %(+)-Z¥\] T8C¡¦§OP¼?@$%Bvw

123234?UV.W/0 X0AD YZ[-  \]^ <_`a +33/Rb> Dcd ef(g E [- ]R- ! \KOP E hiD;KgjfkRO l.m;&' T n*Co /=lPR-6pq;&' T* n*Co /&'rsTtTuT*  ( vwxy.z{0,**0 -|}~) q;&' T* lR-` ;e/Rm0/0 (*./+*.-+*. m,)
Fig. , m6p&'r,sTmax .

)/lP <_`\+31/> //)} +33*   ,**0sTmax 234"*C ,R A, B  /,*- 234?A C )*C

+**C +0 - ! 0 LM34+N D  ,*C /- R6 ,**0  1  )gOO( gO l 
Fig. ,. Temporal changes of sTmax at the thermal
anomaly areas of A (a) to E (e) from +31. up
to +33, and during ,**0. Capitals of A, F, J,K, S in each graph are the initials of thelocations of the ,**0 observations : Arimura,Furusato, Jigoku-gawara, Kurokami and Seto.
Data of +31*s-+33*s are referred from Kamoand Nishi (+31/) and Kamo et al. (+32*, +32,,+320, +322, +323, +33/).

 -.TDmOP. Kagiyama and Hagiwara(+32*) 
Qt<k+k,> ῌ <TuT*> · S<T>T ¡T*-s(,)

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I¤ k+ 6 7 k,  ¥¦§!-P - , W/- 

,**0 m, *C -/ W/m, *C .Q¨©!0 (Sekioka, +32-)R6 ¤ k+, k, }ª«¬­YD  AE  /  (Fig. +b) !

l ®¯! "#$%&' () ,*C +,-.

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; < , 0**2/* m=>=>= A OP

"3vwgv +31.+32- /¶·¸  234?¹ B OP

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< , ./*/** m=>

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E :  C OP6< , -2* m,**0 6p234

Q¨ 2+2 MW ( ?@$µ34OP

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2/* mj)P°±'²(3+1 MW ( A / ±'¢+0- ! 0  LM34+N D O=>

Q /** m ??@?AB=>R6  A / B  Fig. +b STP A, B  - , MW /j)P
+OP !! +* #J?@$%Bvw º/0  234" .9:?AB»¸]^_`ab%cdaef#g124

Fig. -. Combining infrared thermal image with visible image taken from (a) Kurokami, (b) Arimura and (c)Seto. The color scales in the left images show the observed raw temperatures Tobs [C]. Capitals of A-E
mean the ﬁve thermal anomaly areas. Squares drawn by white dotted line are the FOV of right-sided close-up
images. Arrowed anomaly region on a part of Showa Lava in (a) was not clear in +33,.

 A, B,**0  - Tmax  +33,  ! (Fig. ,) +/,*C ,**0  0 "#$%&'(/ "#$%&'()$ *+,45489
-./0/123 ;<6  AC=)$ *+, -./0/123  45 >?@ABC)$DE  

67 489 :F9GH IJ KL MN(OP QRSTG U>V(OP WXST YZ[\qr'^MNO Z[125Fig. .. Distribution patterns of -T at the thermal anomaly areas of A, B and C, during the ,**0 observations.
Contour interval of -T is ,./C. Arrows show the anomaly region on a part of Showa Lava.

 Fig. -  .R%&'() S*+ +33, Xq Fig. -  Fig. . 

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 AC  !"#$ %&' ()*+)z qr{|n}01m ?Fig. .  @AB +33,!"#$,-T ./012

X~DE ^^9:O Z[PZ/E)

345678  A 0 34569:12

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Pq 2
`*!OP AR.RE)2S$P>0T%0U2 (Fig.

 *$gxyQR.RE)2 (Fig. -b)-a) S 'VW ,**0 XY5Z[0\]6~(^: `*lLE

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H$n}()%&' () (Fig. -c)l34;<=Kmn2)Ro)p QR

Fig. . $ Table + K 3

 ,**0 XZ[|h¼bcd¨o$¨I §126

 A CT      0 ! " #$ %&' #()*&+  ,- ./0123456
0ῌ ῎ ῍ ῏,**0 7

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61 ,**0  0 ! " #$&' #&8.
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Kagiyama, T. and M. Hagiwara (+32*) Geothermal survey
in and around O-ana crater and Jodo-daira ﬂat, theVolcanoes Azuma. Bull. Earthq. Res. Inst., //, 02+ῌ1*-.
rstu¨Q­ (+321)+320 ®R# 7
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D7#s ³LC; -+ῌ-0.
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Y:7#s HDp Z 2
D7#s ³LC; -+ῌ-0.
%5µ (,***) % i ¶W <·<¸]VW^¹ pp. -,..
Sekioka, M. (+32-) Proposal of a convenient version of theheat balance technique estimating heat ﬂux on geothermal and volcanic ﬁelds by means of infrared remotesensing. Mem. National Defense Academy Japan, ,-, 3/ῌ+*-.
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