CENOZOIC INTRACONTINENTAL. DEXTRAL. MOTION. IN THE. OKHOTSK-JAPAN. SEA REGION. Laurent Jolivet, Marc Fournier, and Philippe Huchon.
TECTONICS,VOL. 11, NO. 5, PAGES 968-977, OCTOBER 1992 CENOZOIC DEXTRAL
INTRACONTINENTAL MOTION
OKHOTSK-JAPAN
IN THE
SEA REGION
LaurentJolivet,MarcFournier,andPhilippeHuchon D6partement deG6ologie,EcoleNormale Sup6rieure,Paris,France
Eurasia(EUR hereafter).The rotationpole is located in easternSiberia;northof it, extension prevails
alongtheCherskyiranges,andoceanicspreading is activealongtheGakkel-Nansen ridge,whichis the northernmost extension of theMid-Atlanticridge. Savostin et al. [ 1983]insteadproposed dextral motion between the Okhotsk and Amurian blocks
anda kinematic interpretation takingintoaccount the
Vitali S.Rozhdestvenskiy, Konstantin F. Sergeyev,
major structures of northeastAsia suchasthe
Institute of MarineGeologyandGeophysics, Far
Stanovoy ranges(seealsoSavostinandKarasik [1981], andCooket al. [1986]).
and Leonid S. Oscorbin
East ScienceCenter,Yuzhno-Sakhalinsk, USSR
Abstract. A right-lateral shearzonetrending northerly alongmorethan2000kmisrecognized fromcentralJapanto northernSakhalin.It wasactive mainlyduringtheNeogeneandhasaccommodated several hundreds of kilometers of displacement. The
whole structureof Sakhalin is built on this shear
zone.En 6chelonsigmoidalfoldsandthrusts,en
6chelon narrow Miocene basins, anda major discontinuity whichisobserved alongmorethan600 km, theTym-Poronaisk fault,characterize the deformation there.In Hokkaido,en {5chelon folds
andthrusts anda ductile shear zonewithhightemperature metamorphism constitute thesouthern extension of thistranspressional shearzone.It continuesto the southas a zone of transtensional
deformation alongtheeastern margin ofJapan Sea, as en 6chelonbasinsand dextral transferfaults
observed asfar southasNotopeninsula andYatsuo basin.Thestyleof theshearzonethusevolvesfrom transpressional in the northfar from the subduction zone, to transtensionalin the south in the back-arc
region.Strike-slip motionalongthisshearzonewas primarily responsible forthedextral pull-apart opening ofJapan Seaduring theearlyandmiddle Miocene.Dextralmotionis still activein thenorth
alongtheTym-Poronaisk faultin Sakhalinaswell as onthecontinental marginof JapanSea(Koreaand
Asiamainland). Active E-Wcompression replaced thedextral motion along theeastern margin ofJapan
Seain lateMiocene time,andincipient subduction began intheearlyQuaternary. INTRODUC•ON
This active zone extends southwardin Hokkaido
andalongtheeastern marginof Japan Sea.Large shallow earthquakes occurfrequently there(Figures 2 and3); theyareall of reverse faulttypewithE-W direction of compression [FukaoandFurumoto, 1975].Nakamura [1983]proposed thatit corresponds to the southwardextensionof the NAM-
EURplateboundary followingChapman and Solomon[ 1976]. Thisactivezonealsocorresponds to a domain
whichhassuffered deformation sinceOligocene time.Kimuraet al. [1983]proposed thatdextral oblique collision alongtheOkhotsk-Amur plate boundary wasresponsible fortheTertiarystructures, suchas en Echelonfolds in Hokkaido and Sakhalin.
JolivetandMiyashita[ 1985],JolivetandHuchon [1989],andJolivetet al. [1990]showedthatdextral shearcanberecognized alongthecentralbeltof Hokkaido(HidakaShearZone)aswell astheeastern marginof JapanSeafor lowerto middleMiocene time.Lallemand andJolivet[1985],Kimuraand
Tamaki[1986],andJolivet[1986]proposed thatthis
shear zonehasbeen responsible forthedextral pullapartopening of Japan Seain Miocene time(Figure 1).Largedextral motions along N-Strending shear zonesareusuallynot takeninto accountwhen
describing thedeformation ofAsiaexcept byKimura andTamaki[1986],Jolivet[1986],Chenand Nabelek[1988],or Jolivetet al. [ 1990]. In thispaper,wepresent a synthesis of our studies based uponfieldsurveys alongthisactive zonefromcentralJapanto Sakhalin, Landsat
imagery, andfocalmechanism ofearthquakes. Detailed workwillbepublished separately. A new
tectonicmapof theentirefault zoneis described. We
A diffusezoneof activedeformationwith crustal
show thatinMiocene time,structures located along
this2000-kin-long shear zonearecompatible witha
seis. micity runsalong Sakhalin, between theAmur
localizeddextralshearzonewhichevolvesfrom transpressional in the noah to transtensionalin the
various interpretations, theyarediscussed byJolivet
southin theback-arcregion.We discuss itsrelation to theopeningof theJapanSeaback-arcbasin.We alsobrieflydiscuss thesignificance of thedextral
mechanisms,concludedthat a zoneof active compression wasperpendicular to thetrendof
motionsin the overall deformationof easternAsia.
Sakhalin. Theyassigned thisdeformation tothe motionof NorthAmerica (NAM hereafter) relativeto
GENERAL TECTONIC
regionandOkhostkSea(Figure1). It hasledto
etal. [1990].Chapman andSolomon [1976],onthe basis of a study of several largeearthquakes focal
Copyright 1992by theAmerican Geophysical Union Papernumber92TC00337 0278-7407/92/92TC-00337
$10.00
CONTEXT
In theback-arc regionof thePacificsubduction
zone,behind theKuriltrench, Sakhalin isa long islandextending alongsome1000kmbetween the Okhotsk SeaandtheTartarstrait(Figures 1-3).It
doesnotexceed200 km in width andis asnarrowas 30 km at 48øN.It is the northernextensionof the
Jolivetet al.' Motionin theOkhotsk-Japan Searegion
969
EARLY MIOCENE 2O
PRESENT
YBK
PAC
320
•,• PHS• /
1360
/140
1360 I
140OE
Fig.1.(a)Present-day geodynamic context of Sakhalin andJapan Searegion. Shaded
arearepresent theoceanic crusts of theJapanSeaandKurilBasin.Dottedareais thezone
of active compression of theeastern Japan Sea.(b)Same region 20m.y.ago. Reconstruction parameters areafterJolivet etal.[1991]andJolivetandTamaki[1992]. Abbreviations areTPF,Tym-Poronaisk fault;HSZ,HidakaShearZone;MTL, Median Tectonic Line;YBK,YamatoBank;YB, Yamato basin; YF, Yangsan Fault;TB,
Tsushima basin; TF,Tsushima fault;PAC,Pacific plate; andPHS,Philippine Seaplate.
centralrangeof Hokkaidoin northern Japan.It is separated fromtheAsianmainlandby theshallow waterTartarStrait,whichis thenorthernmost partof the JapanSea.To theeast,the OkhostkSeahasa
continental basement cutbynumerous faultsmaking submarine ridgesandtroughs[Marguliset al., 1979; Gnibidenko, 1985].In thesouthern partof the OkhotskSeais theKuril basin,whichis flooredwith
thickCenozoic sediments andoceanic crustpossibly
of Mioceneage[KimuraandTamaki,1985].To the west the Tartar strait is floored with thinned
continental crustcutby N-S trending faultsand blanketed bya thicksedimentary coverupto8 km [Antipovet al., 1980;H. S. Gnibidenko et al., manuscript in preparation, 1992].Furthersouth,the JapanSeaisdividedintothreemajorbasins floored withoceanic crust(Japan basin,deeper than3 km)or highlyintruded thinned continental crust(Yamato
andTsushima basins,deeperthan2 km) [Tamaki, 1985, 1988;Tamakiet al., 1990]. The Kuril trench continues to the south as the
JapantrenchuntilitsjunctionwiththeBonintrench southof thetrench-trench-trench triplejunction between thePhilippine Sea(PHShereafter), Pacific (PAChereafter), andEUR plates[Huchonand Labaume,1989].ThePacificplatesubducts westward at a velocityof about10cm/year[Seno, 1985].ThePhilippine Seaplatesubducts below southwest Japanat slowerrate(4 crn/year)[Ranken et al., 1984;Huchon, 1986].
Activedeformation isrecorded alongtheeastern marginof JapanSea,HokkaidoandSakhalinasa
diffuseseismic zone[FukaoandFurumoto,1975; Tamaki, 1988].Deformationis alsorecordedin the
Tsushima strait[Jun,1990],between Kyushu and Korea,aswellasonthecontinental sideof Japan
970
Jolivetet al.: Motionin the Okhotsk-Japan Searegion 140
145
!
Seain theBohaigulfregionalongmajorstrike-slip dexu'alfaults[ChenandNabelek, 1988].
TheJapanSeaopenedduringtheearlyandmiddle Mioceneaswasrecentlyshownby theresultsof OceanDrillingProgram legs127and128,which encountered oceaniccrustabout20 m.y. old [Tamaki,1990;Suyehiroet al., 1990].Figures2 and 3 showthepositionof sites794, 795 and797 where oceanicbasalticsills were recoveredand dated,with
thecorresponding agesafterKaneokaet al. [ 1992]. In theregionof theu'ench-trench-trench triple junction,theBoninarccollideswith cemxalJapan northof theIzu peninsula, andactiveintraoceanic thrustingoccurssouthof theNankaitrenchalongthe Zenisuridge[Le Pichonet al., 1987;Chamot-Rooke and Le Pichon, 1989; Lallemant et al., 1989; Taira et
al., 1989].Betweenthecollisionzoneandthetriple junction,fight-lateralmotionis activealongthe Sagamitrough.Therelativemotionof PHSrelative to Japanhaschangeddrasticallysince2 Ma [Huchon, 1985; Jolivetet al., 1989]. The direction
of thePHS-EURmotionvectorwasmorenortherly duringNeogeneandthenturnedto NW. We nowdescribethestructures observedalong the entire deformed domain from south to north. We
It.oi:ii L
distinguishtwo zonesof deformation.Oneis the easternmarginof JapanSeasensustricto(northeast Honshu,west Hokkaido, and offshore until Moneronislandwestof Sakhalin);the otheroneis the Central belt of Hokkaido and Sakhalin. EAST JAPAN SEA Late Miocene to Present
E-W compression is activealongtheeastern marginof JapanSea.The mostspectacular evidence is givenby frequentlargeearthquakes andactive
jA PAN % BA S I/v
faults recorded offshore Honshu, Hokkaido, and Sakhalin[Fukao andFurumoto, 1975; Tamaki,
1988].Figures2 and3 showthatthiszoneextends fromtheJapanSeacoastof centralJapanto thewest of Sakhalin.Faultplanesolutions indicateE-W compression andpurereversefaultmechanisms. Theseearthquakes areassociated with N-S trending active reverse faults. These are associated with the
Fig. 2. Tectonicmapof theentireshearzone:1, oceaniccrust;2, en 6chelonextensionalbasinsof
Mioceneage;3, directionof Miocenemaximum compression deducedfrom fault setanalysis;4, sameasfor 3 butintermediate compression; 6, strikeslipfaults;7, thrustfaults;and 8, normalfaults. Abbreviationsare esm, East Sakhalin Moutains; OP,
Oshimapeninsula;O, Ogapeninsula; N, Noto peninsula; IZU, Izu peninsula,TPF, Tym-Poronaisk Fault; MTL, Median Tectonic Line; TI•,
Tanakura
TectonicLine; ISTL, Itoigawa-Shizuoka Tectonic Line; HSZ, Hidaka Shear Zone, and TIT: u'ench• 145
_
u'ench-trench triplejunctionof CentralJapan.
Jolivetetal.' Motionin theOkhotsk-Japan Searegion
971
55
5O
.
4O
55
5O
105
!0
115
12_0
12_5
150
155
140
145
Fig.3.Compilation ofcrustal earthquakes focal mechanisms (compressional quadrant in black).After$avostin etal. [1981],Dziewonski etal.[1983],L. S.Oscorbin
[unpublished data, 1977], Chen andNabelek [1988], Jun[1990]. Shaded area represents
thezoneofE-Wcompression in theeastern Japan Sea. reactivation of Neogene en6chelon basins [Jolivet et
al.,1991].Activethrust faultsupliftnarrow ridges ofoceanic crestsuchastheOkushiri ridge[Tamaki, 1988]. Deepdrilling ontheridgeduring ODPleg 127revealed thatthecoarse-grained detrital supply stops ontheridgeat 1.8Ma because theridgewas upliftedabovethe bottomof thebasinat thistime
[Tamaki etal., 1990].Thisageisinterpreted asthe
inception ofsubduction ofJapan Sealithosphere. Active deformationis observedalsoonlandwhere
Neogene deposits arefoldedwithN-Strending fold axesandthrusts[AmanoandSato,1989;Sato,
1989].Earlystudies of verticalmovements of the northeast Honshu arcreveala periodof upheaval
from5 Matothepresent [Sugietal.,19•3].The paleostress field inferredfrom dike orientation
changes toE-W compression at7 Ma [Nakamura and Uyeda,1980;Takeuchi,1985].Neogene subsidence curveson themarginsof JapanSeaandat oceanic
sitesshow upliftfrom10Matothepresent [Ingle, 1992].Observation offaultsets intheNeogene depositsof westernHokkaidoandnortheastHonshu
indicates a change of maximumhorizontal compression from NE-SW to E-W betweenthe
middleandlateMiocene[Jolivet andHuchon,1989; Yamagishi andWatanabe, 1986;Otsuki,1989].The ageof beginning of E-W compression canthusbe
determinedto have occurredaround9 Ma.
Jolivetet al.' Motionin theOkhotsk-Japan Searegion
972
EarlyandMiddleMioceneDeformation This active deformation reworks a zone of
Miocenetranstension. The en &helongeometryof
Quaternary compressional basins isnotcompatible withthepresent stress field.Because a Miocene grabencropsoutonSadoislandwhichis parallelto theen &helonbasins,it is likely thattheyall
correspond toMiocene extensional basins. Theiren •chelonposition isthencompatible witha dextral obliqueextension [Jolivetet al., 1991].A similar geometry isobserved onlandin theUetsudistrict, wherefastriftingisobserved tohaveoccurred in the earlyMiocene[Yamaji,1989;1990].In general the ageof riftingontheeastern marginof JapanSeais considered tobeearlytomiddleMiocene[Suzuki, 1989;AmanoandSato,1989].The ageof formation of the oceanic basin offshore NE Honshu has been
recently revealed byODPleg 127:atsite794and 797earlyMiocene(20Ma to 16Ma) basalts were recoveredassillsinterbeddedwith deepwater
far south as Honshu. Recent evolution is
characterized byE-W compression andfastupliftof themetamorphic coreof thebelt,theHidaka mountains [Kimuraet al., 1983].SteepN-S trending thrusts separate it fromtheforelandto thewest, whereactivethrusting affectsPlioceneandrecent sediments of theSapporo-Tomakomai depression [Mitani,1978;YamagishiandWatanabe, 1986]. Oligocene toMiddleMiocenedeformation
An olderstageof deformation priorto theE-W compression is recognized onlyin sediments older thanlateMiocene;reverseandstrike-slipfaultsare associated with thisstage[JolivetandHuchon, 1989].The maximumhorizontalcompression trends
NE consistently fromsouthto north.Thisstageis characterized by theformation of NW trending en &helon foldsandthrustsin thenonmetamorphic zones[Kimuraet al., 1983] anda ductileshearzone (HidakaShearZone)in themetamorphic zone.
sediments.Intense basaltic intrusive and extmsive
JolivetandMiyashita [1985]interpreted thisductile
activity,around15Ma, is recognized in theAosawa regiononlandNE Honshu[Tsuchiya,1989,1990]. Faultsetanalysis indicates thatNW-SEextension prevailed withassociation of normalandstrike-slip
deformationasthe resultof dextralshearin a deep crustalenvironment.Jolivet and Huchon [1989]
faults until the end of the middle Miocene in NE
Honshuand Sadoisland [Jolivetet al., 1991].
Additionalobservations confirmthisgeometryin the Notopeninsula andYatsuobasinfurthersouth (Figure3). All faultsetdatafromSakhalinto Yatsuo basinwill bepublished separately [Fournier et al., papersubmitted to Journal of Geophysical Research, 1992].Right-lateral shearis notrestricted tothe JapanSeacoastal area,sinceCretaceous left-lateral shear zones such as the Tanakura Tectonic Line were reactivated in Miocene time as dextral faults
[Koshiya,1986]. The direction of horizontal maximum
compression of Miocene ageremains constant from Yatsuoto Rebunisland,but it corresponds to c2
(intermediate principal stress) in thesouth ando• in
the north. In Rebun island and Hokkaido, NE
trending compression prevails withstrike-slip and
reversefaults [JolivetandHuchon,1989]. To summarize, theeasternmarginof JapanSea wasthesiteof dextralobliqueextension in earlyand middleMiocenetime.Meanwhile,oceanicspreading wasoccurring in YamatoandJapanbasins. By the endof themiddleMiocenea sharpchangein stress fieldoccurred. E-W compression tookplaceonthe samezone.By theearlyQuaternary, subduction began,andthrustfaultsaffectedtheoceanic back-arc region. HOKKAIDO
CENTRAL
BELT
related the en •chelon folds and thrusts and the ductile shear zone to a crustal-scale half flower
structure builtalonga transpressional dextralstrikeslipcrustal faultof Oligocene tomiddleMiocene age. Thisinterpretation is roughlyconsistent withthatof Kimuraet al. [ 1983] in termsof kinematics(dextral obliquecollision). Recentpaleomagnetic
investigations in Hokkaidoconf'mu thisinterpretation [Kodamaet al., 1990].The dextraltranspression is observed till RebunislandontheJapanSeamargin offshore northernmost Hokkaido. East of the
Hokkaidocentralbelt,N-S trendingdextralfaultsare relatedto theformationof smallpull-apartbasinsin Miocenetime[WatanabeandIwata, 1985;Watanabe, 1988]. SAKHALIN
The Hokkaido central belt extends northward
through Sakhalin island.EastSakhalin Mountains is a tectonic mapof Sakhalinderivedfromtheexisting geological mapat 1/1000000scale,Rozhdestvenskiy [1983, 1986],K. F. Sergeyev(unpublished data, 1990) andour own field observations andLandsat imagesanalysis. The mostprominentstructure is the Tym-Poronaisk fault,whichrunsN-S for morethan 600 km. OtherN-S trendingfaultsarerecognized
eastof theTym-Poronaisk fault,buttheyare probablylessactive.FollowingRozhdestvenskiy [1982] andKimura et al. [ 1983] we recognizein Sakhalinthesamedextralstrike-slipdeformation
alreadydescribed in HonshuandHokkaido,butthe recentE-W compression doesnotshowobviouslyin
Late Mioceneto PresentDeformation
the structures.
TheN-S trendingHokkaidocentralbeltwasbuilt throughpolyphase evolutionfromtheMesozoicto thepresent.A drasticchangein thedeformation regimeoccurredat theendof themiddleMioceneas
NeogeneDeformation
Figure4 summarizes theCenozoic structures of Sakhalin,andFigure5 showsthefeaturesseenon
Jolivetet al.: Motionin theOkhotsk-Japan Searegion
973
the Landsat mosaic as well as focal mechanisms of
SCHMID•
shallowearthquakes. The Tym-Poronaisk fault dividesSakhalinin twoparts:WestSakhalin Mountains and East Sakhalin Mountains.
The Cenozoicsequence is roughlysimilaron both sidesof thefault.It beginsin theupperOligocene withcoarseconglomerate andfinesupwardinto lower Miocene sandstone and middle Miocene
siltstone andsiliceous claystone[Melnikov,1987]. The wholesequence is intrudedby basicdykesand sills, and basalticlavas and brecciaconstitutethe end of the middle Miocene. The late Miocene and Pliocene are made of mffaceous siltstone and sandstone.
..
The WestSakhalinMountainsrepresentthe northernextensionof the central belt of Hokkaido; in
generalfaciesaresimilarto thoseof the CentralBelt thoughlessdeepin general[Melnikov,1987].The
Cretaceous isrepresented by forearcdeposits with abundant terrestrial and volcanic detritus. In the East
SakhalinMountains, Cenozoic deposits areundedain by a complexsystem of thrusts slicescomposed of oceanicmaterialof Late Jurassicto Cretaceousage, partlymetamorphosed underhigh-pressure lowtemperature conditions [Rozhdestvenskiy, 1986].G. Kimuraet al. (manuscript in preparation, 1992) describethissystemasa Cretaceous accretionary complex.It is thenorthernextensionof the
_ 500
Kamuikotan
zone of Hokkaido.
Westof thefault andimmediatelyeastof it, Cretaceousand Cenozoic sedimentsare folded; the
NW trendingaxesof the foldsdistributedwith a dextralen6chelonpattern[Rozhdestvenskiy, 1982; Melnikov, 1987]. The folds axes are curvedcloseto
_48
o
o
•'
thefault,thusgivinga sigrnoidalshapecompatible with dextraldisplacement. The faultis a verysharp featureclearlyseenon Landsatimages.The fault planeitselfoccursbetweenCretaceous sediments or lavasandMiocenesandstones. It is usuallya N-S trendingverticalplanewithhorizontalstriationand evidence of dextral motion. In the East Sakhalin
"::i::'t .....-•1
;:•x '"•"
TONINO-
•],.I •-ANIWA PEN.
460 C. KRILION
1420
1440
I
Fig. 4. Tectonicmapof Sakhalinafterthegeological mapof Sakhalin,Rozhdestvenskiy [1982], analysis of Landsatimages(M. Fournieret al., paper submitted to Journalof Geophysical research, 1992) andK. F. Sergeyev(unpublished data,1990). Dashed lines are Cenozoic folds axes seen in the
Cretaceousto Miocene sediments;dottedlines are
axesof postfoliation openfoldsseenin theMesozoic metamorphic complexof theEasternSakhalin Mountains.
Mountains,N-S trendingsteepfaults(Central, Pribrezhnaya, andLimanfaults)cut throughthe Mesozoicaccretionary complex.They areassociated with narrowMiocenesedimentary basinswhichare arrangeden 6chelon.A smalldextralpull-apartbasin is seenon LandsatimagesalongtheNorth-Sakhalin fault.Rozhdestvenskiy [ 1982]showsthatthecontact betweena metamorphic complexand nonmetamorphosed sediments is offsetdextrallyby 25 km. DextraloffsetalongN-S trendingfaultsis alsoobservedin Schmidtpeninsulain thevery north of Sakhalin.
We performedfaultsetanalysisalongandaround theTym-Poronaisk fault.All dataarecompatible with NE trendinghorizontalcompression (Figures2 and5). Faultsetanalysis[Fournieret al., paper submitted to Journalof Geophysical Research,and Figure5] showsanE-W trendingcompression at severalsitesalongthefault,it is howeveralways associated with curved fold axes with the dextral en
6chelonpattern.Thedirectionof compression is
974 1440
elsewhere NE-trending andalwaysperpendicular to foldaxes. E-Wcompression therefore corresponds torotatedsitesandtheoriginaldirection of
compression (Figure 2) wasthusNE.Thisisin goodagreement withthetrendoffoldaxesand SCHMIDT
strike-slipfaults.
Our observations of the deformationin the
accretionary complex below theCenozoic deposits of theEastSakhalinMountainsreveala fu:ststagewith
Fault
Suspected fault
Bedding strike -•
Bedding dip
............. Miocene
•
volcanlcs
Principal stress directions
layer-parallel shear ofprobable Mesozoic age [Kimura etal.,in prep.]followed bya second stage of upright foling.ThesefoldstrendNW andare compatible withthesame NEtrending compression whichgavetheen6chelon foldsofWestSakhalin. We thusattributethesefolds alsoto the Cenozoic
stageandthestrike-slip motion. A recentcompilation of seismic dataallowed H. S. Gnibidenkoet al. (manuscript in preparation,
1992]todrawa precise isopach mapof Cenozoic
•"
+
520
sediments in theTartarStrait.Oneprominent feature
isa deeprhombohedral basin (Figure 2) bounded by NS-trending vertical compressional faultsandNE trending normal faultsandfilledwithmorethan8 km of Cenozoic deposits. Theoverallshape of thebasin and the natureof the faultslead us to the conclusion
thatit corresponds toa dextral pull-apart. Thisshows thatalargepartofthedextral motion waslocalized in the Tartar Strait.
ActiveDeformation
Faultplanesolutions of earthquakes in Sakhalin (L. S. Oscorbin, unpublished data)showtwokinds of mechanisms (Figures3 and5), bothbeing
Fig.5. Mapof Sakhalin showing thefeatures seen
on theLandsatmozaicafterM. Foumieret al. (paper
submitted to Journalof Geophysical Research, 1992).Paleo-stress-field horizontal directions deduced fromfaultsetanalysis areplotted.Fault
planesolutions ofsuperficial earthquakes (depth
lowerthan30 km)determined byL. S. Oscorbin (T-
quadrants inblack), andFukaoandFummoto [1975] (T-quadrants vertically ruled)andcentroid moment tensors determined byDziewonski et al. [ 1985, 1987](T-quadrants horizontally ruled)areshown. Radii of focal mechanismsare a function of the
magnitude (surface waves) ofearthquakes except for
Dziewonskiet al. [ 1985, 1987]. Concerning
Oscorbin data,wekeptthemaineventonlywhen
two focal mechanismswere determinedfor the same
earthquake. Thetwocentroid momenttensors determined byDziewonski et al. [1985,1987] correspond totwoearthquakes whichfaultplane solutions haveindependantly beendetermined by Oscorbin (in orderto simplifyweindicate only Oscorbin's epicenter locations). P axesarealmost similarin eachcase,andT axesof Diewonskiet al.s focalmechanisms aresteeper sothattheyindicate compressional motionwhenOscorbin's indicate strike-slipmotion.
Jolivetet al.' Motion in the Okhotsk-Japan Searegion
compressional: strike-slipandreversefaults.Several mechanisms located close to the main fault trace are
compatiblewith dextralmotionalongthe fault. Rozhdestvenskiy [1986]describes a changein the stresspatternin Pliocenetime from dextralwrench alongtheTym-Poronaisk fault to E-W compression. As describedabove,thefault setanalysisdoesnot revealE-W compression exceptperhapsin thesouth, andall structures observedat largescaleare compatiblewith dextralmotion.The existenceof dextralfaultplanesolutions leadusto thinkthat dextralwrenchis stillactivein Sakhalin,asalready statedby Savostinet al. [1983].
975
Therefore,if the dextral motion is correlatedwith
theJapanSeaopening,severalhundredkilometersof dextraldisplacement areexpected.Reconstructions of thepre-opening situation[JolivetandTamaki, 1992] showa totaloffsetsince25 Ma of about400 km. Thereis no directevidenceconcerningthe total
dextraloffset.OnlyRozhdestvenskiy [1982] describes a 25-km offsetalongonefault in theEast Sakhalin Mountains. As the deformation is
distributed on severalmajorfaultsthetotal displacement is mostlikelymuchlarger.The TymPoronaisk, beingthemajoronshorefault,probably accommodated thelargestdisplacement butcertainly not more than a few tens of kilometers. So, the
DISCUSSION
FromcentralJapanto thenorthof Sakhalin, along morethan2000 km, we recognizea narrowdomain of strain localization with evidence of dextral motion
in Miocenetime.It is thusa majorfeatureof the deformationof easternAsia, and it is worth
discussing its evolutionwith time. Present-DayActivity
AlthoughE-W compression is obviousin the south,in theback-arcregion,with numerouslarge compressional earthquakes andothercompressional features,it is not as clear in the north. Dextral
motionisprobablystillactivein Sakhalin,exceptin theverysouth(theMoneronearthquake is similarto thoseoff HokkaidoandHonshuandcorresponds to thenorthernmost extensionof theEastJapanSea nascentsubductionzone).
MioceneDeformation
In thenorththestrike-slipdeformation is transpressional andlocalizedalonga very narrow zone,characterized by en 6chelonfoldsandthrusts andonemajordiscontinuity, theTym-Poronaisk
fault.Furthersouthit becomes moretranspressional in the Hidaka mountains where the shear zone curves
towarda morewesterlytrend.Ductilepartsof the shearzonewerethereupliftedduringthedextral shear.Thistranspressional zonecontinues in the southwest asa transtensional onealongtheeastern marginof JapanSea.It is characterized by en 6chelongrabenanddextraltransferfaultswhichwere laterreactivated ascompressional structures. The dextralshearin HokkaidoandJapanSeamargin endedabout10 m.y. agoandis contemporaneous withthedeposition of earlyto middleMiocene sediments. It is thusexactlycontemporaneous with theopening of JapanSea.Figurelb showsa reconstruction of thestrike-slip shearzonein early
Miocene t/meduringanearlystageof JapanSea opening[afterJolivetet al., 1991;Jolivetand Tamaki,1992].It is contemporaneous with the
rotation of SWJapan deduced frompaleomagnetic data[Otofujiet al., 1985].The dextralshearzone extends to the south as a dextral fault between SW
JapanandKorea [Sillitoe, 1977].
largestpartof thedextralmotionmustbe takenup alongtheTartar Straitwherethecrustis thinner. It is noticeable that the dextral shear zone is
nowherecompatible with thePAC-EURrelative motion.Furthermore,it extendsnorthwardvery far from the subduction zoneandtrendsat a largeangle to thetrenchsystem.It is thusunlikelythatit represents a back-arcstrike-slipfault suchasthe Philippineor Sumatrafaultswhichaccommodate the obliquityof themotionvector[HuchonandLe Pichon,1984].Suchobliquityis observedin the Kuril trenchat presentandis accommodated by a ENE-WSW dextralfaultparallelto theKuril arc, whichcutsthrougheasternHokkaido[Kimura, 1986].It is almostperpendicular to thetrendof the majordextralshearzone. The dextral shear zone was turned into a
compressional zonein theback-arcregionabout10 m.y. ago.This datecorresponds to the end of the JapanSeaopeningandis slightlyyoungerthanthe arrivalof thetriplejunctionin itspresentposition [Jolivetet al., 1989].The compression is restricted to theback-arcregionnorthto thecentralJapantriple junction.Far off thetriplejunction,eitherin Sakhalin or in Korea,andalsoon thecontinental sideof Japan Sea,thedeformation is stilldextral(Figure3) [Chen andNabelek,1988;Jun,1990].Southof thetriple junction,extensionis activein theBoninarc.This suggests thatcompression is dueto thelocalplate configuration in thetriplejunctionregionand/orthe degreeof platecouplingalongthesubduction zone andis notcharacteristic of themoregeneraltectonic contextof easternAsia.FollowingKimuraand Tamaki[1986]andJolivetet al. [1990],we suggest thattheSakhalin-East JapanSeais oneof themajor dextralfaultscreated in theAsiancontinent during theIndia-Asiacollision.Figure3 showsthatother dextralfaults whichare still active,existwestof it. ChenandNabelek[1988] showedthatdextral motionhasbeenactivein theBohaigulfregionalong NNE trendingfaults.Jun[1990] describes focal mechanisms alongtheTsushima faultwhichare compatiblewith dextralshear.This shearzone reactivated in Miocene time the Mesozoic suture that
runsalongHokkaidoandSakhalin.Far fromthe subduction zoneit was,andstillis, a transpressional wrench fault, and it turned to a transtensionalone in
theback-arc regionbecause extensional tectonics was prevailingthere.At thattimeall majorback-arc
976
Jolivetet al.' Motionin theOkhotsk-Japan Searegion
basinswereopening(JapanSea,Shikokubasin, SouthChinaSea,andpossiblyKuril basin),which
Aknowledgements: Specialthanksaredueto Helios Gnibidenko,RimmaKovalenko,andOleg
indicates that extensional conditions were active all
Melhnikov
alongthewesternPacificmarginbehindthe subruction zone.The formationof thisstrike-slip shearzonedisturbedtheback-arcextension,giving riseto thepull-apangeometrywe nowobserve. Extensionin theback-arcregionwaslinkedwith the mechanics of stress couplingalongthesubruction zone,andstrike-slipwith internaldeformation of
Sakhalinsk, andfor field guidanceanduseful comments.We alsowishto expressour thanksto GakuKimuraandKoji Okumura,who wereour pannersduringthe field surveyin Sakhalin.This studywasfundedby CentreNationalde la Recherche Scientifique-Institut NationaldesSciences del'Univers(programme Dynamiqueet Bilande la Terre,DBT). Thispaperis DBT contribution 417.
Asia due to collision with India.
for their warm welcome in Yuzhno-
REFERENCES Amano,K. andH. Sato,Neogene tectonics of the centralpartof northeast Honshuarc,Mem. Geol. Soc.Jpn.,32, 81-96, 1989.
Tamaki,K., Suyehiro,K., Allan,J. et al., 1992, Proc.ODP,Sci.Results, 127-128,in press, 1992.
Kodama,K., T. Takeuchiand T. Ozawa,
Palcomagnetism of EarlyCretaceous to Neogene deposits in CentralHokkaido,Japan:block Antipov, M.P.,V.M. Kovylin,and V.P.Filat'yev,Jolivet, L., America-Eurasia plateboundary in rotationcaused by strike-slip faultmovement (abstract), EosTrans.AGU, 71 (28), 865, 1990. Sedimentary coverof thedeepwaterbasins of eastern Asiaandthe opening of marginal Koshiya,S., TanakuraShearZone,the deformation Tatarstrait andthenorthern partof theseaof basins. EarthPlanet.Sci.Lett.,81,282-288, Japan,lnt. Geol.Rev.,22, 1327-1334,1980. 1986. process of faultrocksandits kinematics, J. Chamot-Rooke, N., andX. Le Pichon, Zenisu Jolivet,L., and P. Huchon, Crustal scalestrikeGeol. Soc.Jpn.,92, 15-29, 1986. ridge:mechanical modelof formation, slipshearzonein Hokkaido, Northeast Japan, Lallemand,S., andL. Jolivet,JapanSea,a pull
Tectonophysics, 160, 175-194,1989. Chapman M. C.,andS. C. Solomon, North
J. Struct. Geol.,11,509-522,1989. apartbasin, EarthPlanet.Sci.Lett.,76, 375Jolivet, L., andS.Miyashita, TheHidaka Shear 389, 1985. American-Eurasian plateboundaryin northeast Zone0tokkaido, Japan), genesis during a right- Lallemant, S.,N. Chamot-Rooke, X. LePichon,
Asia,J. Geophys.Res.,81,921-930, 1976. Chen,W. P. and J. Nabelek,Seismogenic strikeslipfaultingandthedevelopment of theNorth China basin,Tectonics,7, 975-989, 1988. Cook, D.B., K. Fujita, andC. A. Mac Mullen,
Presentdayplate interactions in northeast Asia: North America, Eurasianand Okhotsk
plates.J. Geodyn.,6, 33-51, 1986. Dziewonski,A.M., A. Friedman,D. Giardini,and
J.H. Woodhouse, Globalseismicityof 1982: centroid moment tensor solutions for 308
earthquakes, Phys.Earth Planet.lnt., 45, 1136, 1983.
Dziewonski,A.M., J. E. Franzen,and J. H.
lateral strike slipmovement, Tectonics, 4,289-
andC.Rangin, Zenisu ridge: a deep intraoceanic
302, 1985.
thrustrelatedto subduction, off Southwest
Jolivet, L.,andK.Tamaki, Neogene kinematics in Japan, Tectonophysics, 160,151-174, 1989. theJapan searegion andvolcanic activity ofthe LePichon, X.,J.T. Iiyama, J.Boul•gue, J. northeast -Japan aro,In Tamaki,K., Suyehiro, K., Allan, J. et al., 1992,Proc. ODP, Sci.
Results,127-128, in press,1992. Jolivet,L., P. Davy, andP. R. Cobbold,Rightlateral shearalongthe northwestPacificmargin and the India-Eurasia collision, Tectonics,9, 1409-1419, 1990.
Jolivet,L., P. Huchon,and C. Rangin,Tectonic settingof westernPacificmarginalbasins, Tectonophysics, 160, 23-48, 1989.
Charvet,M. Faure,K. Kano,S. Lallemant,H. Okada,C. Rangin,A. Taira,T. Urabe, andS. Uyeda,NakaitroughandZenisuridge:a deepsea
submersible survey,EarthPlanet.Sci.Lett.,83, 285-299, 1987.
Margulis,L.S., Mudretsov,V.B., Sapozhnikov, B.G., Fedotov,G.D. & Khvelauk,I.I., 1979, Geologicalstructure of thenorthwestern partof the sea of Okhotsk.lnt. Geol. Rev., 22, 10941102, 1979.
Woodhouse, Centroid-moment tensorsolutions Jolivet,L., P. Huchon,J.P. Bran,N. ChamotMelnikov,O.A., Structureandgeodynamics in Rooke, X. Le Pichon and J.C. Thomas,Arc HokkaidoandSakhalin,in Russian,Nauka, 95 for October-December 1984,Phys.EarthPlanet. deformation and marginalbasinopening;Japan Inter., 39, 147-156, 1985. pp., 1987. Seaasa casestudy,J. Geophys. Res.,96, 4367- Mitani, K., Changingof the Tertiarysedimentary Dziewonski,A.M., G. Ekstrom,J. E. Franzen,and 4384, 1991. basins in the western flank of the axial belt of J. H. Woodhouse, Globalseismicityof 1979: centtold-moment tensor solutions for 524 Jun,M. S., Sourceparameters of shallowintraplate Hokkaido-beatinga significance of the earthquakes in andaroundtheKoreanpeninsula earthquakes, Phys.Earth Planet.Inter., 48, 18Sunagawalowlandto UmaoiHilly belt,Assoc. andtheirtectonicimplication, Acta Univ. Ups., 46, 1987. Geol.Collab.Jpn.Monogr.21, 127-137, Comp.Sum.of UppsalaDiss.Fac. Sci., 285, 16 1978. Fukao,Y., andM. Fummoto,Mechanisms of large earthquakes alongthe eastemmarginof the
pp., 1990.
Japan sea,Tectonophysics, 25, 247-266,1975. Kaneoka, I., Takigami, Y., Takaoka, N., Gnibidenko,H. S., The Sea of Okhotsk-Kuril
islandsridgeandKuril-Kamchatka trench,in The OceanBasinsandMargins,vol. 7A, edited
by A.E.N.Naim et al., pp.377-418,Plenum,
Yamashita,S. and Tamaki, K., 40Ar-39Ar analysesof volcanicrocksdrilled from the
JapanSeafloorby Legs127/128,In Tamaki, K., Suyehiro,K., Allan, J. et al., 1992, Proc.
ODP, Sci.Results,127-128,in press,1992. andcollision; Huchon, P.,Grodynamique dela zonedecollision Kimura,G., Obliquesubruction forearctectonics of the Kuril arc,Geology,14, d'IzuetdupointtripleduJaponCentral,Th•se New York, 1985.
de Doctoral,Univ.Pierreet Marie Curie,Paris, 414 pp.,1985. Huehon,P., Commenton "Kinematicsof the
Philippine seaplate"by B. Ranken,R. K. CardwellandD. E. Karig.Tectonics, 5, 165168, 1986.
Huchon, P.,andP. Labaurae, Central Japan triple junction:a three-dimensional compression model,Tectonophysics, 160, 117-133, 1989. Huchon,P. andX. Le Pichon,Sundastraitand
404-407, 1986. Kimura,G., andK. Tamaki,Tectonicframeworkof the Kuril arc since its initiation,in: Formation
of ActiveOceanMargins,editedby N. Nasuet al., pp. 641-676,Terrapub, Tokyo,641-676, 1985.
Kimura, G., and K. Tamaki, Collision,rotationand
backarc spreading; thecaseof theOkhotskand Japanseas,Tectonics,5, 389-401, 1986. KimuraG., S. Miyashita,andS. Miyasaka,
CentralSumatra Fault, Geology,12, 668-672,
Collisiontectonicsin Hokkaido and Sakhalin,
1984.
in Accretion Tectonics in theCircum-Pacific Regions,editedby M. Hashimoto andS. Uyeda, pp. 117-128,Terrapub,Tokyo, 1983.
Ingle,J. C., Subsidence of theJapanSea:evidence fromODPsitesandonshore sequences, In
Nakamura,K., Possiblenascenttrenchalongthe
eastern Japanseaas theconvergent boundary betweenEurasiaandNorthAmericanplates(in Japanese with Englishabstract), Bull. Earthquake Research Inst.Univ.Tokyo,58, 721-732.
1983.
Nakamura, K. andS. Uyeda,Stress gradient in backarcregions and platesubduction, J. Geophys.Res.,85, 6419-6428, 1980. Otofuji, Y., T. Matsuda,andS. Nohda, Palcomagnetic evidences for the Miocene counterclockwiserotationof northeast Japan-
riftingprocess of the Japanarc,Earth P!anet.Sci.Lettt., 75, 265-277, 1985. Otsuki,K., Reconstruction of Neogenetectonic stress field of Northeast Honshu arc from
metalliferous veins.Mem. Geol. Soc.Jpn.,32, 281-304, 1989.
Ranken,B., R. K. Cardwell,andD. E. Karig,
Kinematics of the Philippine seaplate. Tectonics, 3, 555-575, 1984.
Rozhdestvenskiy, V. S., Theroleof wrenchfaults in the structure of Sakhalin,Geotectonics, 16, 323-332, 1982.
Jolivetetal.'Motionin theOkhotsk-Japan Searegion Roz.hdestvenskiy, V. S., Evolutionof the Sakhalin Suzuki,K., On the LateCenozoichistoryin the southernpart of northeastHonshuin Japan, fold system,Tectonophysics, 127, 331-339, 1986. Mere. Geol. Soc.Jpn.,32, 97-112, 1989. Sato,H., Degreeof deformation of Late Cenozoic Taira,A., H. Tokuyama,andW. Sob,Accretion stratain the NortheastHonshuare, Mere. Geol. tectonicsandevolutionof Japan,In The Evolutionof thePacificOceanMargin,edited Soc. Jpn.,32, 257-268, 1989. by Z. Ben-Avraharn, pp. 160-123,Oxford Savostin, L.A.,andA.M. Karasik, Recentplate tectonics of the Arctic basin and of UniversityPress,100-123,New York, 1989. Takeuchi,A., On theepisodic vicissitude of northeastern Asia, Tectonophysics, 74, 111145, 1981.
Savostin,L., L. Zonenshain,and B. Baranov, Geologyandplate tectonics of theSeaof
Okhotsk,in: Geodynamics of the Western Pacificand IndonesianRegion,Geodyn.Ser., vol. 11, W.C.T. Hilde andS. Uyeda,pp. 343354, AGU, Washington, D.C., 1983.
Seno,T., Is NorthernHonshua microplate?, Tectonophysics, 115, 177-196,1985. Sillitoe,R. H., Metallogeny of an Andean-type continental marginin SouthKorea, implications for opening of theJapanSea,in IslandArcs,DeepSeaTrenches andBackArc Basins, MauriceEwingSet.,vol. I, editedby
tectonic stress field of the Cenozoic northaest
Watanabe,Y., andK. Iwata,The ageof the MioceneKamishiyubetsu formationin northern Hokkaidoandthe basinsformedby tectonic movements, J. Geol. Soc.Jpn.,91,427-430, 1985.
Yamagishi,H., and Y. Watanabe,Changeof stress field of Late Cenozoic
Southwest
Hokkaido,Japan,- investigation of geologic faults,dykes,ore veinsandactivefaults, Monogr.Geol. Collab.Jpn.,31, 321-332,
Honshuarc,Japan,in Formationof Active OceanMargins,editedby N. Nasuet al., Terrapub,pp. 443-468,Tokyo,, 1985. Tamaki,K., Twomodesof backarcspreading,
Yamaji,A., Geologyof theAtsumiareaandEarly Mioceneriftingin the UetsuDistrict,Northeast Japan,Mere.Geol. Soc.Jpn.,32, 305-320,
Geology,13, 475-478, 1985. Tamaki,K., Geologicalstructure of theJapansea andits tectonicimplications, Bull. Geol. Surv.
Yamaji,A., Rapidintra-arcriftingin Miocene northeast Japan,Tectonics,9, 365-378,1990.
1986.
1989.
Jpn.,39, 269-365, 1988.
Tamaki,K., Proc.OceanDrillingProgramInitial Rep., 127, 1990. Tsuchiya,N., Submarinebasaltvolcanismof Miocene Aozawa formation in the Akita-
M. Talwani and W.C.Pitman 11I,pp.303-310,
Yamagata oil field basin,back-arcregionof Northeast Japan,Mere.Geol.Soc.Jpn.,32,
AGU, Washington, D.C., 1977.
399-408, 1989.
Sugi,N., K. Chinzei, andS. Uyeda,Verticalcrustal Tsuchiya, N., MiddleMiocene back-arc rift movements of northeast JapansinceMiddle magmatism of basaltin theNE Japan arc,Bull. Miocene. in:Geodynamics of theWestern Geol.Sum.Jpn.,41,473-505,1990. Pacificand lndonesian Region, Geodyn. Ser., Watanabe, Y., Deformation structure of the vol.I 1,W.C.T.HildeandS.Uyeda, pp.317Uenshiri horstin theHidaka belt,Central 329,AGU,Washington, D.C., 1983. Hokkaido, J. Geol.Soc.Jpn.,94, 527-533, Suyehiro, K.,etal.,Proc.Ocean DrillingProgram 1988. Initial Rep.,128, 1990.
977
M. Fournier,P. Huchon,and L. Jolivet,
Drpartement de G6ologie,EcoleNormale Suprrieure,24 Rue Lhomond,75231 Pariscedex, France.
L. S. Oscorbin,V. S. Rozdhdestvenskyi, and K.F. Sergeyev, Instituteof MarineGeologyand Geophysics, Far EastScienceCenter,YuzhnoSakhalinsk, USSR.
(ReceivedJanuary23, 1991; revisedDecember18, 1991; acceptedFebruary10, 1992.)
