 3¹ º .1 » .3ῌ/0 ,**- DJapanese Journal of Structural Geology, No. .1, .3ῌ/0, ,**-E

Internal Structure and Permeability of the Yanagase Fault

 *ῌ *
Keiji Sato* and Akito Tsutsumi*
Abstract : We investigated the internal structure and permeability of the YanagaseFault, an active fault in SW Japan, at two localities, Kamishimizu in Fukui Prefecture
and Nakakawachi in Shiga Prefecture, through ﬁeld survey and laboratory measurements. The Yanagase Fault of the studied area is developed in the Jurassic accretionary complex of the Mino-Tamba Belt. In both outcrops, the Yanagase Fault
consists of - zones : fault gouge zone, fault breccia zone and host rock. Permeability of
the core samples from the fault outcrops was measured with a gas-medium tri-axial
deformation apparatus using a pore-pressure oscillation method. Test results performed at 3* MPa e#ective pressure indicate that the highest permeabilities are foundin the fault breccia zone and the lowest permeabilities in the host rock. In theKamishimizu outcrop, permeability is +*+1-+*+0 m, for the fault breccia, +*+3-+*+1 m,
for the fault gouge and +*+3 m, for the sandstone host rock. In the Nakakawachi
outcrops, permeability is +*+2-+*+1 m, for the fault breccia and +*+2 m, for the fault
gouge. The permeable nature of the fault breccia zone of the Yanagase Fault is similar
to the previously reported permeability structure of the fault developed within agranitic basement rock.
Key words : Yanagase Fault, permeability, fault rocks, active fault῍ !"#$%$&' ()*῍+,ῌ
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School of Science, Kyoto University, Kyoto 0*0ῌ2/*,,Japan

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E  q /£  f !"=IG&¤ ,*¢6_¥¦§O# |,Af#h  ¦§O# &'e! +./ m g &D!  aGhi¦§Ojk#,Y¨K©ªm5 mmw5 cm n«¬2=Cl­fo<* f2   +./ m g &®! ¦§O pq­ ¯r<°ª¦m +*w -* cm 7 q ¦§O§Oe\±sr<e1hi $²!
 ³ª t³ª u³ª<Nlv &! 1wx yµ<xz¶
1´e

Fig. +(a) The distribution of active faults aroundthe study area, SW Japan.
(b) Localities of theKamishimizu and Nakakawachi outcrops (·) along thenorthern part of the Yanagase Fault.
Based onSugiyama et al., (+33.).

¼ 50 ¼Z[ .1 '(R Z[Fig. ,A photograph (a) and a sketch (b) of the Kamishimizu outcrop. Open circles represent thesampling points for the permeability measurements.

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YZNOP-!NOP%0 56
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Fig. A photograph (a) and a sketch (b) of the Nakakawachi outcrop. Open circles represent thesampling points for the permeability measurements. The stereogram shows equal-area, lower hemisphere
projections of the fault plane (great-circles) and striations on the fault plane (arrows).

 52 /h.1 »º#+*+,          
 + m    !"#  $  #%&'()* + , 
-. 
/!"0#
123,m 8  4)50+6  7$%9&6 1* cm  #
' (:);6/!<6#*+,-);"=>.?@/0) Fig. , A
B Fig. - C Faulkner and Rutter D+332E 2M ,* mm F1)GH 6 I&JK&L
31N3O4 2M ,/ mm PQ&%P1N3O)
5#= 67 A# R891N3O)
:S ;6<; =>6 TU>.)?@6= VWX YZ[=\? TU>.  @\?] ;6A2"<B "^ L_`&a3# I&bc3d3C DeEfF(6 g hG$ "i   2*j kHlI);= mnVW 5#=F(g>.]S. +* mm Jg , *+,->W  oKpPqr - ]L(ῌ+M>Ws)5#= VW tXuv ;# NqABwῌqOP QRP+6= kHxyzQ
R U{|&"}S~TyP)5#=*+,-D+y>WE  M UtVPWTX#++Fig. .

- YZ+.w[.+\  0yP)=-$ ]0 *+V^_+6  yP)VP+65#=VW3  M)5#=`+ab ^+c kHyP)wῌVP+65#+^$]0  +y>W);"=g a>. +M>W);" );U+ dM+wῌe+f5>.*+,)g+)&'+6=VWc+"0  wῌqhi1 DKranz et al.,*+,-+33* ; Fischer and Paterson, +33,E )5#= 1  >. V jklPqm)noL<.=+ vV jkl qmLi)6 hUABf*+, jk%"}MI%)!-1  DFig. .E  VWp hU+f)' qF1@+  *+, jk%L<) '!+¡r+#^]0 mn wῌqhi1 5#=wῌq s-  ,* MPa tuwῌqLi  h +
6 >. VMPa 8v ¢ *./,+*** s I`&o+6=
VWp v£q DNqῌwῌqE  wM67>.
;6 ¤ 3* MPa p¥#67>. ;6 ¤ +2* MPa i x¦' y§. D¨D©qEqE g -* MPa i ©ª.+*+, v£Nq)zt=   {0<« |}) ,.1 g/cm- +6 wῌMq ~Mq )¬6=­® 3* MPa v£q /v /km E. f ±. ,,0 mm ²T>.2¯°4³K´%µ¶&1N3O)%·¸56#¹2¯°4)5#=+M>W­®  

Schematic illustrations showing the pore pressure oscillation method.

¼ 53 ¼µ¶·¸ῌ¹ º»

+333   -* MPa  !"#  $%&' ()*+ ,-. /0$1
2 3456 78 9:();< =>?@<A' B
,-<C' D 2 37 EF <GH IJ.KLMN1 2+ 
OPQ RST'U?@()VWX<Y
Z. Fig. / a2 [\] ^_=>`a=>b cde ?@f gh' [$ 3* MPa i +*j+3k+*j+0 m, ;'U2[:gl Bm?@[$ -* MPa  nop4q. B
$Dr stu Ov'Uwxw_U2 .Dsy
=>`a =>b f gl9i?@<nz{|'
1 2 ?@ }7g~u 4q. $ i?@;4q. BDu_U2   %
' D ?@ [:v ^_ gh' 3* MPa i B R()
f +*j+3 m, ;$mU2 'U?@glnop4qt =>`a =>b cde # 
$Hm 2, RST'U?@()VWX<YZ. Fig. / b2 =>b cde    [glVWX$STLDu_U
2 [\]
UHvl#Z'^_=>`a =>b ?@f gh' [$ 3* MPa i ?@$ +*j+1 k+*j+2m, ;'U2 ?@ }7f [\]f gh'   9 [ +2*MPa i  +*j+3k+*j+2 m, ;gh'U2[gl `a?@\l x ?@
f~uD¡L4q \] 'U2  [$ -* MPa <¢ £ ¤¥ ?@; nop$¦mt
9?@<{|'B$su 2 Bm`a?@ }7g~u 4q. $ i?@;4q. B
Du_U2- OPQ R  R x §¨=>?@[: 3* MPa ?@< Z'
©ª<U Fig. 02 BY «¬ => ­®. 2 OPQ¯°< ±¬ ?@<_R =>`a?@$ +*j+3k+*j+1 m, =>b ²$ +*j+1k+*j+0 m, ;<Z' =>`a$stuD$m ?@<Z.¡¯$HmU
Fig. 0 a2  nop  %' D ?@ +*j+3 m,  ()f ;D_U2  R=>³e´=>`a$ +*j+2 m, ;<Z' }=>b +*j+2 k+*j+1 m, nz;<Z'U Fig. 0b2Fig. /Permeability of the fault rocks at the Kamishimizu (a) and the Nakakawachi outcrops (b), plotted against thee#ective pressure.

¼ 54 ¼

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XY +@%?

Fig. 0
Variation of permeability at the Kamishimizu (a) and the Nakakawachi outcrops (b) across the Yanagase Fault.
Permeability of each sample at 3* MPa e#ective pressures are plotted against the distance of the sample point across the fault.

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 eRf+gR+?
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Zhi !
 ; b"῍ H§¨ a87 ª£D 3* MPa +«+u£¬+ +?
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    &'( )* )+, - ῍. /0, /01'2 3456
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Antonellini, M. and Aydin, A., +33., E#ect of faulting on ﬂuid ﬂow in porous sandstones : petrophysical properties. Bull. Amer. Assoc. Petrol.
Geol., 12, -//ῌ-11.
Evans, J. P., Forster, C. B. and Goddard, J. V., +331,
Permeability of fault-related rocks, and implications for hydraulic structure of fault zone.
Jour. Struct. Geol., +3, +-3-ῌ+.*..
Faulkner, D. R. and Rutter, E. H., +332, The gas permeability of clay-bearing fault gouge at ,*[,in Fault. In Jones, G., Fisher, Q. and Knipe, R. J.,
eds., Fault Sealing and Fluid Flow in Hydrocarbon Reservoir., Geol. Soc. Spec. Pub., +.1ῌ+/0.
Fischer, G. J. and Paterson, M. S., +33,, Measurement of permeability and storage capacity inrocks during deformation at high temperatureand pressure. In Evans, B. and Wong, T. -F.,
eds., Fault mechanics and transport properties ofrocks., Academic Press, +21ῌ,++.
4\] +332 5^67 _5^6 `8abc7d e'9Ifgh +* p.
L*MN ,**, :;f<=7 >?'ijk
lm-@nAoB Cp f qDrE s
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x!"yF +33+ zFG% xfHIA
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Kranz, R. L., Saltzman, J. S. and Blacic, J. D., +33*,
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