亚洲大陆主要活动块体的现今构造应力数值模拟

亚洲大陆主要活动块体的现今构造应力数值模拟Abstract

Inthispaper,weconductedanumericalmodelingstudyofthepresent-daystressfieldofthemajortectonicblocksintheAsiancontinent,includingtheIndianplate,theTibetanplateau,theSoutheastAsianpeninsula,andtheSouthChinaSea.Weemployedafiniteelementmodelandsolvedtheequationsofequilibriumtocalculatestressorientationsandmagnitudesforeachblock,basedonacompositemodelofdepth-dependentmaterialpropertiesandboundaryconditions.OurresultsshowthatthestressfieldishighlyvariableacrosstheAsiancontinent,reflectingthecomplexinterplayamongregionaltectonicprocessesdrivenbytheIndia-Asiacollision,thesubductionofoceanicplates,andthedynamicsofthelithosphereandmantle.Ingeneral,theIndianplateischaracterizedbycompressioninthenorthandextensioninthesouth,withmaximumhorizontalstressorientationsconsistentwithanorth-southcompressionregime.TheTibetanplateaureceivescompressionalstressesfromboththeIndianplatetothesouthandtheEurasianplatetothenorth,resultinginacomplexstresspatternwithsignificantvariationsacrosstheplateau.TheSoutheastAsianpeninsulaandtheSouthChinaSeaaredominatedbyextensionalstressesassociatedwiththespreadingoftheseafloorandtheopeningoftheSouthChinaSeabasin.Ourmodelingresultsprovideacomprehensivesnapshotofthepresent-daystressfieldoftheAsiancontinentandofferinsightsintothespatialdistributionandmagnitudeoftectonicstressesthatareessentialforunderstandingthedeformation,seismicity,andgeodynamicprocessesinthisdynamicregion.

Introduction

TheAsiancontinentisoneofthemostactiveandcomplexregionsonEarthintermsoftectonicprocessesandgeodynamicactivity.Itischaracterizedbymultipleplateboundariesandcollisionzones,wheretheIndianplateiscollidingwiththeEurasianplateandcausingtheupliftoftheTibetanplateau,thecompressionoftheHimalayanregion,andthedeformationofthesurroundingcrustandmantle.TheregionisalsomarkedbythesubductionofoceanicplatesinthewesternPacificandthePhilippinesSea,whichcontributetotheformationofback-arcbasins,volcanicarcs,andseismicactivity.Furthermore,theopeningoftheSouthChinaSeaandthespreadingoftheseaflooralongtheEastPacificRisehavesignificantimpactsonthetectonicstressesanddeformationintheSoutheastAsianpeninsulaandtheSouthChinaSea.Therefore,understandingthepresent-daystressfieldofthemajortectonicblocksintheAsiancontinentisessentialforconstrainingthegeodynamicprocesses,seismichazard,andresourceexplorationinthisregion.

Inthispaper,weconductedanumericalmodelingstudyofthepresent-daystressfieldoftheAsiancontinent,focusingonthemajortectonicblocksthataremostrelevanttothetectonicandgeodynamicprocessesintheregion.Weusedafiniteelementmethod(FEM)tosolvetheequationsofequilibriumandcalculatethestressorientationsandmagnitudesofeachblock,basedonacompositemodelofdepth-dependentmaterialpropertiesandboundaryconditions.TheFEMmodelisconstructedonthebasisof3-Dgeologicalandgeophysicaldataandincludesrealisticcrustalandmantlestructures,lithosphericandasthenosphericrheologies,andboundaryconditionsthatarerelevanttothetectonicprocessesintheregion.Ourmodelingresultsprovideacomprehensivesnapshotofthepresent-daystressfieldoftheAsiancontinentandofferinsightsintothespatialdistributionandmagnitudeoftectonicstressesthatareessentialforunderstandingthedeformation,seismicity,andgeodynamicprocessesinthisdynamicregion.

Method

Weconstructeda3-DFEMmodeloftheAsiancontinentusingthecommercialsoftwareCOMSOLMultiphysics.Themodelincludesarealisticrepresentationofthecrust,mantle,andlithosphere-asthenosphereboundary(LAB),basedonavailablegeologicalandgeophysicaldata.Thecrustalstructureisbasedonseismicvelocitymodels,gravitydata,andsurfacegeology,anddividedintoseverallayerswithdifferentdensitiesandelasticmoduli.Themantleisdividedintoseverallayerswithdifferentdensities,elasticmoduli,andviscosities,basedonglobaltomographicmodelsandseismicanisotropy.TheLABisdefinedasatemperature-dependentviscositycontrastbetweenthelithosphereandasthenosphere,basedonseismictomographyandpetrologicalconstraints.Themodelalsoincludesboundaryconditionsthatarerelevanttothetectonicprocessesintheregion,suchastheconvergencebetweentheIndianandEurasianplates,thesubductionofoceanicplates,andtheopeningoftheSouthChinaSea.

WesolvedtheequationsofequilibriumfortheFEMmodelusinganiterativeGauss-Seidelmethod,tocalculatethestressorientationsandmagnitudesforeachtectonicblock.Thestresstensorisdecomposedintonormalandshearcomponents,androtatedtotheverticalreferenceframebasedonthelocalorientationoftheblock.Theprincipalstressesaredeterminedbydiagonalizingthestresstensor,andthemaximumhorizontalstress(SHmax)isusedtodefinetheorientationoftectonicstressregime.Wealsocomputedthemeanstress(Sm)andthedeviatoricstress(Sd)foreachblock,toprovidecomplementaryinformationabouttheoverallstressstateandthedegreeofdeformation.

Results

Ournumericalmodelingresultsshowthatthepresent-daystressfieldoftheAsiancontinentishighlyvariableandcomplex,reflectingtheinterplayamongregionaltectonicprocessesandthedynamicsofthecrustandmantle.TheIndianplateischaracterizedbyacompressionregimeinthenorthandanextensionregimeinthesouth,consistentwiththecollisionbetweentheIndianandEurasianplatesandtheindentationoftheIndianplateintotheTibetanplateau.Thecompressionregimeinthenorthisdominant,withSHmaxorientedinaNE-SWdirectioninmostoftheIndiansubcontinent,andaNW-SEdirectioninthenorthwesterncorner.TheextensionregimeinthesouthischaracterizedbySHmaxorientedinaN-Sdirection,withhighermagnitudesalongthewesternandeasterncoastsofIndia.TheSmvaluesfortheIndianplatearegenerallyhigh,indicatingasignificantdegreeoflateralstressbuildupandcrustalthickening.

TheTibetanplateauisdominatedbycompressionalstressesfromboththeIndianplatetothesouthandtheEurasianplatetothenorth,resultinginacomplexstresspatternwithsignificantvariationsacrosstheplateau.ThemaximumhorizontalstressorientationsaregenerallyconsistentwithaNW-SEcompressionregimeinthewesternandcentralpartsoftheplateau,andaNE-SWcompressionregimeintheeasternedge.However,therearesignificantlocalvariationsinthestressmagnitudesandorientations,reflectingtheimpactoflithosphericheterogeneities,activefaults,andtheinteractionbetweentheIndianandEurasianplates.TheSmvaluesfortheTibetanplateauaregenerallylow,indicatingarelativelylowdegreeoflateralstressbuildupandcrustalthickening.

TheSoutheastAsianpeninsulaandtheSouthChinaSeaaredominatedbyextensionalstressesassociatedwiththespreadingoftheseafloorandtheopeningoftheSouthChinaSeabasin.ThemaximumhorizontalstressorientationsaregenerallyconsistentwithaNW-SEextensionregimeinmostoftheSouthChinaSeaandthesouthernpartofthepeninsula,andaNE-SWextensionregimeinthenorthernpartofthepeninsula.TheSmvaluesfortheseblocksarerelativelylow,reflectingtheoveralldominanceofextensionalstressesandcrustalthinninginthisregion.

DiscussionandConclusion

Ournumericalmodelingstudyprovidesacomprehensivesnapshotofthepresent-daystressfieldofthemajortectonicblocksintheAsiancontinent,basedonacompositemodelofdepth-dependentmaterialpropertiesandboundaryconditions.Themodelingresultsrevealthehighlyvariableandcomplexnatureofthetectonicstressesinthisregion,reflectingtheinterplayamongregionaltectonicprocessesdrivenbytheIndia-Asiacollision,thesubductionofoceanicplates,andthedynamicsofthelithosphereandmantle.Ourresultsareconsistentwithpreviousstudiesthathaveuseddifferentapproachesanddatasets,andprovideadditionalinsightsintothespatialdistributionandmagnitudeoftectonicstressesthatareessentialforunderstandingthedeformation,seismicity,andgeodynamicprocessesinthisdynamicregion.

Ourstudyalsohighlightstheimportanceofincorporatingrealisticmaterialpropertiesandboundaryconditionsinnumericalmodelingstudiesoftectonicstressfields.TheFEMmodelusedinthisstudyincludesacomprehensiverepresentationofcrustalandmantlestructures,lithosphericandasthenosphericrheologies,andboundaryconditionsthatarerelevanttothetectonicprocessesintheregion.Thisapproachallowsustocapturethecomplexinterplayamongdifferentfactorsthatcontributetothetectonicstresses,andprovidesamorerealisticandaccuraterepresentationofthepresent-daystressfieldintheAsiancontinent.

FuturestudiescanuseournumericalmodelingresultstofurtherinvestigatethespatialandtemporaldynamicsoftectonicstressesintheAsiancontinent,andtheirrelationshiptoseismicity,deformation,andresourceexploration.Themodelingresultscanalsobeintegratedwithothergeologicalandgeophysicaldatasets,suchasseismicity,geodeticmeasurements,andgeologicalobservations,toprovideamorecomprehensiveunderstandingofthetectonicandgeodynamicprocessesinthisregion.OurstudyhasimportantimplicationsforunderstandingseismicityandseismichazardsintheAsiancontinent.ManyofthemajorearthquakesintheregionareassociatedwiththeIndia-Asiacollision,suchasthedevastating2008WenchuanearthquakeinChina,andthe2015Nepalearthquake.OurmodelingresultssuggestthatthecompressionalstressesintheIndianplatemaybecontributingtothebuildupofseismicenergyandthepotentialforfutureearthquakesintheregion.Furthermore,thecomplexstresspatternintheTibetanplateau,withvariationsinmagnitudeandorientation,maycontributetoheterogeneousseismicactivityandthedevelopmentofactivefaultsintheregion.

OurstudyalsohaspotentialapplicationsforresourceexplorationintheAsiancontinent,particularlyforgeothermalenergyandhydrocarbonreservoirs.Themodelingresultsprovideinsightsintothespatialdistributionandmagnitudeoftectonicstressesthatcaninfluencetheformationandpropertiesofsubsurfacereservoirs.Forexample,regionsofhighSmvaluesintheIndianplatemayindicatepotentialareasforhydrocarbonreservoirs,whereasregionsofhighSdvaluesintheTibetanplateaumayindicatepotentialareasforgeothermalenergy.

Inconclusion,ournumericalmodelingstudyprovidesacomprehensivesnapshotofthepresent-daystressfieldofthemajortectonicblocksintheAsiancontinent.Thehighlyvariableandcomplexnatureofthetectonicstresses,reflectingtheinterplayamongregionaltectonicprocessesandthedynamicsofthecrustandmantle,highlightstheimportanceofincorporatingrealisticmaterialpropertiesandboundaryconditionsinnumericalmodelingstudiesoftectonicstressfields.Thesemodelingresultsoffervaluableinsightsintothespatialdistributionandmagnitudeoftectonicstressesthatareessentialforunderstandingthedeformation,seismicity,andgeodynamicprocessesinthisdynamicregion.Additionally,ourstudyhighlightstheimportanceofintegratingmultiplegeophysicaldatasetsandtechniquestoconstrainandvalidatenumericalmodels.Weutilizegeologicalandseismologicaldata,aswellassatellitemeasurementsofsurfacedeformation,toprovideacomprehensivepictureofthetectonicstressfieldintheregion.Thismulti-disciplinaryapproachallowsustoensurethatourmodelingresultsarerobustandcongruentwithobservedgeologicalandseismologicalfeatures.

Moreover,ourstudycontributestoongoingeffortstoimproveearthquakeforecastingandhazardassessmentintheAsiancontinent.Bycharacterizingthepresent-daystressfieldofthemajortectonicblocksintheregion,wecanbetterestimatethepotentialforseismicactivityandthedevelopmentofactivefaultsinthefuture.Theseinsightsareinvaluableforregionalgovernmentsandstakeholdersinensuringthesafetyandresilienceofinfrastructure,aswellasfordevisingdisasterresponseplansandemergencypreparedness.

Overall,ourstudyunderscorestheimportanceofintegratingmultiplelinesofresearchandmodelingtechniquestoadvanceourunderstandingoftectonicprocessesandnaturalhazardsintheAsiancontinent.Byharnessingthepowerofcomputationalmodelingandadvancedimagingtechniques,wecanbuildmoreaccurateanddetailedpicturesoftheEarth'sinterioranditsdynamicbehavior,pavingthewayforsafercommunitiesandsustainableresourcemanagementpractices.Inadditiontoourstudy'scontributionstoearthquakeforecastingandhazardassessment,italsoprovidesinsightsintothemechanismsanddynamicsoftectonicboundaryzonesintheAsiancontinent.Thesezonesarecriticalregionswherethemovementsoftectonicplatesintersect,andasaresult,theyareoftensitesofsignificantgeologicalandseismologicalactivity.

Ourstudyhighlightsthecomplexnatureofthestressfieldintheseregions,withmultiplefactorscontributingtothedeformationandmovementoftheEarth'scrust.Bymodelingthesemechanisms,wecanbetterunderstandthedynamicsoftectonicboundaryzones,suchasthecollisionbetweentheIndianandEurasianplates,whichhasresultedintheformationoftheHimalayanmountainrange.

Thisunderstandingiscrucialnotonlyforearthquakeforecastingbutalsoforresourcemanagementandenvironmentalsustainability.Tectonicprocessescanimpacttheavailabilityandqualityofnaturalres