'( J. Hot Spring Sci. /3 -0ῌ./ ,**3ῌ῎῎῍ῑΐῌῒ῏ῐ "  + ,+,

  ,+

+-

/

,*



Temperature Structure under the Kinki Area,
the Southwest Japan Subduction Zone
Yoshitsugu FURUKAWA+

Abstract
In the southwest Japan subduction zone, the temperature structure has been estimated using observed surface heat ﬂow data. In the estimations, the crustal temperature
is higher in the volcanic belt along the Japan sea, and is lower between the trough andthe volcanic front due to the subduction of the cold oceanic plate, which is considered to
be a common feature in subduction zones. In this subduction zone, higher heat ﬂow isobserved in the belt where the forearc basins are located, which is considered to be caused
by upward ﬂow of accreted materials in the belt of the accretionary prism, which is induced by the interplate coupling equivalent to a back-slip of *.*-/ m/yr. In the region
between the volcanic front and the forearc basins, local higher and lower heat ﬂow anomalies exist. These could be caused by local upheaval, subsidence, and heterogeneity ofradiogenic heat generation in the crust. In this study, temperature anomaly due to these
thermal disturbances is estimated. The result shows that the estimated heat ﬂow values
agree with the observed ones and temperature di#erence caused by the disturbances isless than about 0*& at a depth of +* km.
Key words : temperature structure, Southwest Japan arc, upheaval-subsidence, radiogenic
heat generation, back-slip῏῍)*+,- ./+01234567'8+9:;< =>?@+ABCD'8EFG.HIJGKLCDMNONP+QRSTUVWXYZ[\'B ]^_`HabcGMNO
defgVW_hijkl^[m'BnDhi5[nop<^i5[ q6=>?@BcGm'cr[Gs+t/HuBc\5012vwxl^i5[ yz{cGMNOdefgVW_[|}W_`~v 1i5[nop<^ ]^W W_`+012++36 0*0ῌ2/*,  !"#$% + Division ofEarth and Planetary Sciences, Graduate School of Science, Kyoto University, Kitashirakawa
Oiwake-cho, Sakyo-ku, Kyoto 0*0ῌ2/*,, Japan.

 /3

,**3



  

!"#$ %&'()*+, - ./  0123$ $4356789:;< ='>;<$:
?$ &@56A B +* km C 0* DCE'FGHI : 4  J,ῌ- /  KLMNLO+    APQR!

P

STSP"A8$

 U#V4$%W(  &,XY(AZ'[&\]^$ STS_'(_`>(:CEGiggenbach, +33, a (_#CEBlattner, +33- )b* +c

,$^A   &,Xa defgh+)7FijC D4
7-?'A./kCE A J[0(lm nopq^$qrN
fnOsoD#tuC ?! eovMw ?xyx

D

47z1('23$ .aSfo+j24A _P"c{CA V|aQRP" /3}4)!
! !

1P"k ~fo)+& 9'23$

1P"*v,: J7:#t#5CAD4

F D4FA6C=.

(^( =~Mo.V=7UA#V CE
C=:'?^$F::xCyx

=(  8$

4$
89CA 
D4

!" %&a;4!"

8i

, 



.

A<=@m6<9V CEm >41'<=?C3$ 

FA $ ,  7i n@CA AnBCD4E:U m F7(417 (:~fO+74CD<=?7i 

FA D_)D1"@<=GHa6I) 4

/¡ DB2,&( 4/¡)¢J'  n@BCA?!  ¢J./£C U m B4C¤KC417i?'C : n@OsoAL¥ M¦Cw@$ 7§ ¨M

+ ©ª«+C + ¬NNOCOso47Fi?'CE .P.AQ­
CEm ®a¯4/¡ D_") ¢J56R°C '23$ $
7 ±V£V(DB2 ²S7: AUT m @mB³NfT´74417µ9
U3¶L¥ M¦ 

1VW7·. Sfo+C<=723:w> Sfo+,&i6<C <=@9_X¸.¹<?' .¹ -*ῌ.* km CE'i'6CYZA , [j' m<=7ºi¶6CU» km M¼+D VWA.,&i'23$ :.P.CA <=?a/  )

1VW01 .V : &"@

"R°C '23$  ! Q­ 7·.CA 1½
37






!"#$% & '()
*++,-. km $,/0

123 456 

7 +** km 8

9: ;&#<16+=>?
@ABCD#E&F8#$
GHIJ6K, L7%+
 7+  MN7O23 P L3$,/0*&+7Q !" 7  &'#$R7O23


Fig. + a #ST7UV03B

WX Furukawa et al., +332
YZ2[Z# \]
GH^VM_`a#+bUc +de+1 fB O-. km 8 g7R
bUhi2<jMkj1 :l#
8 * M=>?mn7O+#ee 7L8op*7:& '() J6123
q7rsZ2op
Fig. + Observed heat ﬂow in and around the Kinki area
(after Furukawa et al., +332). (a) Heat ﬂow distribution. Contours of the heat ﬂow value are also shownwith the interval of ,* mW/m,. The dotted line denotes the trench. (b) Heat ﬂow proﬁle in the direction perpendicular to the trench, in which heat ﬂow
in the rectangle shown in (a) is used. Anomalously
high heat ﬂow data associated with local hydrothermal activity is neglected. VF, SP, FB and T indicate
the volcanic front, the Sanyo province, the forearc
basin, and the Nankai trough, respectively.

& 'L3t3^VX+J1M
uvwq&&GH^VXBA#++kx yz{ST+ |}~7
d1hMLZ2 #Z56J 
Z2u|!#Z 6X1
561 ST+ u#
J6K, LC#+>|?M71 7+|#"#GHMXMe  7R |?#"GHM
# Taira, ,**+

RkfZ#+u#" J61 ST¡$|#¢£X Fig. + b #WX YZ2 u¤¥
#+ - <d%qM¦§J61M¨ 32+|?}1 u|!q

|}~#J61
fB©ªMª&q7+«¬1#d1Mk­1g#®¯XBA

Fig. + 7+°±d²³?J6 3 3+´µ&7¶©·¸#$
%BA7O, DGHIJBR7+1 - km 8  ;&'()¹ºBA#+ 'i +** m 7¹»M(  ¼2 ,**0



7+$,kj1*7 GH#<16½)X7 ´&& '(
38

 /3

,**3



'()* !"#$ %&+ ,- ./012#34

5$67"8.

=#

"'()> -*ῌ.* mWῌm, ,- ./012#+** mWῌm, ?@6

 345$ Furukawa/0129:




;(<

and Uyeda, +323 &A)B6 !ACDE2FῌGHIJK-L&M<E2F A
 NO!M<D&6 PM<D Furukawa, +33-
:': &+# ./012'()

 "#QRS67

6TCD $U00VWX2 Y#Z[#\] %^) BM< #./012%&'_S&6`(a)'(b*/ +/ c,/def+gh./i./01

26<= %<A]")#

j-M< 0VWX2i.:klmnopnq2Ars'/'( t$#ef 2* mWῌm,?@5

'(")uDQR: /* mWῌm, #"dFurukawa, +333 ; Wang et al., +33/ & Fig. + b 

j-M<vwxy#\ ./012'("'Dz{08E2F#|+r@}iK-L&S~$$ ef+A]$%<A]5X z#1A#\6(<# 23A]2CD6(<[ 48 4/54A] =<Z (< =z{0'(5 @}:D$Z %&##r'(j-M<A]

5

6 =$U0e6#  7`:D[ $:D 8(<D] %&# 51i;&6 `( & 0VWX2
@95 "'(!CDM< ]`M< U8FE/i:C
D"7`:#\6(<D &; < xi < NS^ $U0e#5

vwM<D6(<D Yamano

et al., +33,¡ ¢£=+#5 !ACD¤4M<#5 <A#\&6 P¥M<D t$£#"#*$95):D] ¦>+- §¨M<D "#:5{0©ª¡< z{0#?¨«@iAC¬@}:D6(<D Davis et al., +32- ;Platt, +320 =g­# ®¯"#:x{0©ª¡<?¨B @}:CD`:D] ") EF ° Taira, ,**+ &<(GL¤4H0VWX2#\6(< !A±UI²A]³´
 µ´?§A5 < ¶ %@} +#  A] NM< C#5

6:DvwM<D67·I´ (< Furukawa, +333

vwJK

$C-]:%<?¸+$¹'

Tº+

S

%<(¹D»¼#½LS

39





-ῌ ῑ῎῍ῒ῏ῐ  !"#$ %&'()*+,$-./0*01
2#3456789:; <=>?@A !$ 4BC80/"#DE/0;
4FGHIJKLJK +** km MNOPQRS1*T UV/4WX,*Y
Z[\]*4^X,_`a4bcdef$ghDE; ijkl"#DE/0;>?@AmnD -* km BC8 Fig. , op Furukawa, +33/a qrJK +** km
s[]Ntum^*vw8x;q1yz; qBC$m$ + {|#}~8
2#3/DE 7 7,$9DE/0*0 qr$nD -* km $ .**ῌ0** T 4BC83/1*;*V/0;
>?$/;0

[dy7

7 

#p;q1y.

q$^*7 7 !8x;q1yz; Fig. , $ ¡¢£ -** JKa 2** ¤1¥0PQs[]¦+3/0;q1y§J; ¨m$ 0 [d©; ª ©T«£$¬­d]®©;4 ¯y
!8°±3/0;19:KE/0;²³>?$>?¡´µ 0** Nt1¶·^ay"#DE/0;²³>?Z

­dyq¸;1p;1 7 7^* !89p;1q¸«£y¹ºp;q1y»¼DE;=>?¡½^4y +** mWῌm, TnDy 2** M;q189p;1Fig. , Temperature distribution at the depth of -* km in and around Japanestimated from observed heat ﬂow (after Furukawa, +33/b). The contour
interval is ,**. Higher heat ﬂow contours along the Nankai trough areprobably due to thermal disturbances in the crust.

40-* km >?¡´µ$¶·^y0²³>?1a /3  ,**3

 !"# $#%&!'()*+,-./0123456 -* km 78/ 0** ῌ
2** 9 :   : / 0   ; < = #  2*mWῌm, >?@A:2 Fig. - >3A

1:BC>DE/FAGH*2
I
J K/L=# > M >NOPOQ/DRSQ =T> UVKDNO
PWXYZ) [>\]
^>_`I >abKRScd()\6
Te/,-. fD gh/ijk-l>\!/0m
n+.o g7p'()*: 2
q4;<=# RScd()\6
Te/

+ /* mW ῌ m, 9:/0;< 78 -* km /:D1r/BCstu9: -**ῌ.** 9:/0;<=# J K\6.D NOP
Wcvwx(XYZ)y+zo [{|+}8I~/0 \6Te/DNOPWXYZ)+AI~: D\6>+ :4D1: >?@A9:/0;<=# I 1: DNOPO2;4I:BC|!

Fig. - Calculated temperature-depth proﬁles. The
temperature proﬁle in the crust with the radiogenic heat production for the surface heat ﬂow
of /* mW/m, : no upheaval (+) ; upheaval of +mm/yr (,) ; the subsidence of + mm/yr (-) ; higher
heat production and no upheaval (.) ; higher heatproduction and the upheaval of + mm/yr (/). Thatwith no upheaval for the surface heat ﬂow of 2*
mW/m, (0).

&-/0 Furukawa, +333 ; Hacker et al.,,**- ; Wang et al., +33/^>_`I > VK/ xZDh #>\!/01+3
#>\ +NOPWXYZ)>\6

8# Furukawa, +333

 *.*+ mῌyr :/7>$6P#;<

8#I f+Fm/

01+38# 6ab/-wXD C6+
4!

NOPO:2 *.*./ mῌyr 4 *.*-/ mῌyr /01234e D +ῌ, mmῌyr 9:6 :
:!"HZ Hasebe et al., +33-

1%&

Furukawa, +333 

=BC4I: &-/0

19::: >#< ¡D¢9:/0£¤¥¦I~C§¨©>5U + ª«/$¬2;< ­®*¯Z%°D
k

d,T
dT kH
u

*
dz
k
dz,

 11/ T D: z D78 k D±²'ij:/0 ±²Cermák and Rybach, +32,

³´

k D³´

H D& u Dµ¶·fD#¸# *.2+*0 m,ῌs, ,./ WῌmK 4I¥¦I~ 11/j:D¹º0D»¼:k4½C4 ()D§> z* /0A IVK/BC8#Igh: 2;4 (
41





 ,*
! ,* km  -,*   "# $  %&'( )*+, +./ mWῌm- - Yamaguchi et al., ,**+ ./&' Fig. - 0
1 " * 23 " /* mWῌm, #4 56789:;<=>?@8 523 ,* ῌkm A84 B& + km  .*km  +**mWῌm,

 8  1

 .

 " + mm ῌ yr  , mm ῌ yr 23  ,C'D'  1* 3/ mWῌm, 84 E0&'F-GHI6,J5"K

 5'L23 B& +* km 1"!-23"MNF -*ῌ0*

"OP84 +**B&" +ῌ, km QP8
RSTU?VGHI6WX YLZ[\[-X-PZ]O6"^_NF- 5'LXG`$  abX#c!L' dZe#fNF $ $gf%7+"c!L' hi$gf U Th.*

K "jkFl4 d&himn'h"O-5"oL'F- pqr(mstuvw)n'h"xPNFl4 C'L ]L*yz S+z S{z|&'F- Ishihara, +31-
5'Ln'hz$gf%, *yz)*hi,,#" S+z*yz"MNF ,ῌ- -\[8,0 Ishihara, ,**- ; i}L ,**/
n'h* . B&X~c!L'F- Furukawa, +33/b
55 O," +* km B&)*hi,p N
B& z km  H mWῌm- w#L
Hz,.*ezῌ+*+./5-Ftu./  0/ mWῌm, 84 S+z%&'"MO-p-,8 ./&' Fig. - 0 523 1 "+ mmῌyr 2318N23mW80E`b 55 NF- 5B&
 /0Wc!123

#c!L'

pq456b4"&'c!L'Fl4 78 +302 +**ῌ,**23W#'Yp-tu8kF-5"&' 
\[8 1 NFl4 ¡"p-8kF-6"#'YC¢£!¤[8-X8#¥ 9!Y \¦:"M§-"%&'F- Fig. + 5' ¨©8b¢£#c!L' *./ῌ+ mmῌyr  $6ª«<¬ +303 c!'Y%,"J[ 523B& +* km  -*§8 Fig. - 5S;­L'"MO-, $ $gf%7+®¨©81 $6ª«<¬ +303 ¢£bX#]XN'8- $gf"\[P ]Z + mmῌyr 1NF-
 2/ mWῌm, 84 ¯°8-X%&'F-O±²³p-,8 523 +* km  /*O84 +**

B& ,ῌ- km 8

Fig. -Figure - I´µ6¶vX0NF- I´µ$B.

·?V1aO"&' GH6¶v5'L ab4O
P8X 6¸$B.¹Y8- 5'L ac<'YGH6X
B& ,ῌ- km " +**w²8" ,**w² +* km B&b4XBP8º'Y=N8- 5O»¼Nc!L'½"­L''Y C42 /3  ,**3

 !"#$"%&'()*+,-.$/ !" 0)12) +** km 34567&'(89:;

<$!*,-%=>)?" @ABCD!*E%FGF+=> $ HIJKLM7%NO7%!"+PQ)FGFRS+TU"$ VV7&W)FGF+XY)Z[\]9=>$ ^_/ + `abcde)FGFf+Z[
E=>$E FGFfg)h@Ai"\C78jk% FGFElmnop+qU
7#$Erst)u7$ Turcotte and Schubert, ,**,









 
VV7 r %v c %h L %w Tm %FGF8 T* %lm8 w %FGFfg
T

 y %FGFfx t %yz7#$ /ῌ+* km 9=> +/*

lm) +,***



FGF+Z[E.$E {8jk% Fig. . )!$ V|}7% r, c, L 9{ ~,,1** kgῌm- +., kJῌkg -,* kJῌkg E V|}7% + `abcde9rsA @A"89>$E=> $+  + uD)%VFGFfg7% *./ῌ+ Myr
7{8% ,**tE!$ {km 7#$

&()FGF)@$hD8*9=>$\] :

)@$8

+A% FGFf:z)FGFZ[+b "VE+$ $ p s   $p  )¡¢ῌ£ ¤¥o¦ §¨eo FGFZ[D©ª)«"=¬  ­v+®"/ V  p ¯zjk°e ±E¡²±%?  9³s.$VE%" { DY´9 ).$/)% { ~ ¯z3456)µUt °¶·¸D¹º+» E!$7#¼½

Fig. . Calculated temperature anomalies caused by a intrusion of magmain the shallow crust. The solid lines and dashed lines represent thetemperature proﬁle for the thickness of the intrusion of , km and + km,
respectively. The numbers denote the time (million years) after the
intrusion.

43





.ῌ ῎ ῍ ῏ !"#$%&'()* 
+ ,-./0123456789:'7898;<= > ?@7898;A%B?%+CD;%EFG 1HI JAKL=1MNOA'P"#$QRS('ATU > ?@VW"#$QT*( X

+ -* km Y

1HI 0**ῌ2**KL=1MN -**ῌ.**Z""6[\ ] X > ?%7898;^ 1MACD,_05
`OA'PXA+ab@'c?J'+

d!ef05g%Gh+@i dj?klm<ATU nW1J;+ 7
89o2345%LS(pbqXrstuv%Lqlm<ATU(' ]KL=WNwx?@c?J'y%&'( Kzk%&'(T{* X+ d|}~%L}e @q 7%Llmh*@' XlmQ^hS X+y% .* mWῌm, jlmQ
U6!"lm+ +* km Y 0*

ff%LS( ,**Z"!<ATU ]

Z"j"%@%+djff6 !`%qX@@@'ATU ""+ wx?@#$QbJi+@' KQ%G%+ `4g% ¡"¢ !
#$e £¤ ?¥¦6#<ΐῒ

$% , &'&¦(§+?¨@©ª05Q'«b ¬$QL=­%GXA6b ])®¯°±²j³´µ¶%+¦(Z·*%¸ *('«' X%¹º'*]Gῐ῕῔ῑBlattner, P. (+33-) : “Andesitic water” : a phantom of the isotopic evolution of water-silicate
systems. Comment on “Isotopic shifts in waters from geothermal and volcanic systems
along convergent plate boundaries and their origin” by W.F. Giggenbach. Earth Planet.
Sci. Lett., +,*, /++ῌ/+2.
Cermák, V. and Rybach, L. (+32,) : Thermal properties. In G. Angenheister, Ed. Physical Properties of Rocks, VIb, pp. -*/ῌ.2+. Springer-Verlag, Berlin.

 d+,»¼g42 +303 :  d+,½ »¼ 1 +2,ῌ+21.
Davis, D., Suppe, J. and Dahlen, D.A. (+32-) : Mechanics of fold-and-thrust belts and accretionary wedges. J. Geophys. Res., 22, ++/-ῌ++1,.
Furukawa, Y. (+33-) : Depth of the decoupling plate interface and thermal structure underarcs. J. Geophys. Res., 32, ,***/ῌ,**+..
Furukawa, Y. (+33/a) : Vertical distribution of heat generation in the Nissho granitic pluton,
Hokkaido, Japan. Geophys. Res. Lett., ,,, 1++ῌ1+..
Furukawa, Y. (+33/b) : Temperature structure in the crust of the Japan arc and the thermal
e#ect of subduction. In M.L. Gupta, and M. Yamano, Eds. Terrestrial Heat Flow and Geothermal Energy in Asia, pp. ,*-ῌ,+3. Oxford and IBH Publishers, New Dehli.
44 /3  ,**3

Furukawa, Y. (+333) : Interplate coupling and deformation in the accretionary prism in theSouthwest Japan subduction zone. Geophys. Res. Lett., ,0, -+./ῌ-+.2.
Furukawa, Y., Shinjoe, H. and Nishimura, S. (+332) : Heat ﬂow in the southwest Japan arc andits implication for thermal processes under arcs. Geophys. Res. Lett., ,/, +*21ῌ+*3*.
Furukawa, Y. and Uyeda, S. (+323) : Thermal state under the Tohoku arc with considerationof crustal heat generation. Tectonophysics, +0., +1/ῌ+21.
Giggenbach, W.F. (+33,) : Isotopic shifts in waters from geothermal and volcanic systems along
convergent plate boundaries and their origin. Earth Planet. Sci. Lett., ++-, .3/ῌ/+*.
Hacker, B.R., Peacock, S.M., Abers, G.A. and Holloway, S.D. (,**-) : Subduction factory ,. Are
intermediate-depth earthquakes in subducting slabs linked to metamorphic dehydration
reactions? J. Geophys. Res., +*2, ++.
Hasebe, N., Tagami, T. and Nishimura, S. (+33-) : Evolution of the Shimanto accretionary complex : A ﬁssion-track thermochronologic study. In M.B. Undrewood, Ed. Thermal Evolution of the Tertiary Shimanto Belt, Southwest Japan : An Example of Ridge-Trench Interaction, p. +,+ῌ+-0. Geol. Soc. Am., Boulder.

 +302 :    !"# $%&' %&() 1 ,.2ῌ,0*.
Ishihara, S. (+31-) : The Mo-W metallogenic province and the related granitic provinces. Min.
Geol., ,-, +-ῌ-,. (in Japanese with English abstract)
Ishihara, S. (,**-) : Chemical contrast of the Late Cretaceous granitoids of the Sanyo and
Ryoke Belts, Southwest Japan : Okayama-Kagawa transect. Bull. Geol. Survey Japan, /.,3/ῌ++0.

*+,- ./01 23 4 ,**/ : 56789:;<= <>?@=AB$CD
EABFG  HIJ()KL /0 3-ῌ32.
M N O PQ RS ,**0 : TUVWHVWX: /0 -ῌ+/.

Platt, J.P. (+320) : Dynamics of orogenic wedges and the uplift of high-pressure metamorphic
rocks. GSA Bull., 31, ++*0ῌ++,+.
Taira, A. (,**+) : Tectonic evolution of the Japanese island arc system. Ann. Rev. Earth Planet.
Sci., ,3, +*3ῌ+-..
Turcotte, D.L. and Schubert, G. (,**,) : Geodynamics. Cambridge University Press, Cambridge.
Wang, K., Hyndman, R.D. and Yamano, M. (+33/) : Thermal regime of the Southwest Japansubduction zone : e#ects of age history of the subducting plate. Tectonophysics, ,.2, /-ῌ03.
Yamaguchi, T.I., Yamano, M., Nagao, T. and Goto, S. (,**+) : Distribution of radioactive heat
ﬂow production around an active fault and in accretionary prisms of southwest Japan.
Phys. Earth Planet. Inter., +,0, ,03ῌ,11.
Yamano, M., Foucher, J.-P., Kinoshita, M., Fisher, A., Hyndman, R.D. and Party, O.L.S.S. (+33,) :Heat ﬂow and ﬂuid ﬂow regime in the western Nankai accretionary prism. Earth Planet.
Sci. Lett., +*3, ./+ῌ.0,.

45