学科分类
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872 个结果
  • 简介:TheChi-Chiearthquakein1999causeddisastrouslandslides,whichtriggerednumerousdebrisflowsandkilledhundredsofpeople.Acriticalrainfallintensitylineforeachdebris-flowstreamisstudiedtopreventsuchadisaster.However,settingrainfalllinesfromincompletedataisdifficult,sothisstudyconsideredeightcriticalfactorstogroupstreams,suchthatstreamswithinaclusterhavesimilarrainfalllines.Ageneticalgorithmisappliedtogroup377debris-flowstreamsselectedfromthecenterofanareaaffectedbytheChi-Chiearthquake.Thesestreamsaregroupedintosevenclusterswithdifferentcharacteristics.Theresultsrevealthattheproposedmethodeffectivelygroupsdebris-flowstreams.

  • 标签: 聚类分析 河流 地震 泥石流 统计学
  • 简介:Thehorizontalaccuracyoftopographicdatarepresentedbydigitalelevationmodel(DEM)resolutionbringsaboutuncertaintiesinlandscapeprocessmodelingwithrasterGIS.Thispaperpresentsastudyontheeffectoftopographicvariabilityoncell-basedempiricalestimationofsoillossandsedimenttransport.AnoriginalDEMof10mresolutionforacasewatershedwasre-sampledtothreerealizationsofhighergridsizesforacomparativeexamination.EquationsbasedontheUSLEareappliedtothewatershedtocalculatesoillossfromeachcellandtotalsedimenttransporttostreams.ThestudyfoundthatthecalculatedtotalsoillossfromthewatersheddecreaseswiththeincreasingDEMresolutionwithalinearcorrelationasspatialvariabilityisreducedbycellaggregation.TheUSLEtopographicfactors(LS)extractedfromappliedDEMsrepresentspatialvariability,anddeterminetheestimationsasshowninthemodelingresults.ThecommonlyusedUSGS30mDEMappearstobeabletoreflectessentialspatialvariabilityandsuitablefortheempiricalestimation.TheappropriatenessofaDEMresolutionisdependentuponspecificlandscapecharacteristics,appliedmodelanditsparameterization.ThisworkattemptstoprovideageneralframeworkfortheresearchintheDEM-basedempiricalmodeling.

  • 标签: GIS 数字模拟 动力效应模型 土壤损失
  • 简介:Localscourmayoccurwhenahydraulicstructureispositionedinachannelwithanerodiblebed.Herewithinvestigatedexperimentallyaretheerosionandflowpatternduetoawaterjetpassingoverachannelbedattheasymptotic(final)state.Thedevelopmentofthescourhole,itsmaximumscourdepthandlength,arerecordedandcomparedwithavailablescour-depthrelations.Twosetsofexperiments(seeTable1)werecarriedout.Set1(3runs)wasconcernedwithmeasuringtheverticalinstantaneousvelocitydistributioninthescourhole.Thescourholeattheasymptotic(final)state,t≈100[h]wasinvestigated.Set2(5runs)wasconcernedwithstudyingthephysicsofscouring.Thescourholeataboutmid-state,t≈0.5[h],wasinvestigated;subsequentlythescour-holedepthwaslinearlyextendedonthesemi-logscaleto72[h];novelocitymeasurementswereperformed.Thepresentdataareputincontextwithsome(popular)existingrelations;recommendedisamodificationofsomeoftheserelations.

  • 标签: 局部冲刷 侵蚀 流线谱 冲刷深度 预报
  • 简介:Laboratoryexperimentsonlongitudinaldispersioninclear-waterandsediment-ladenopenchannelflowsarereported.Datafromtheseexperimentsandthoseavailablefrompreviousstudiesindicatethatthesuspendedsedimentpresentintheflowaffectsthelongitudinaldispersionprocess.Theobservedvelocitydistributionsoverthedepthofsediment-ladenflowsindicatethatthevelocitydeviatesfromthemeanvelocitymoreinsediment-ladenflowsthaninclear-waterflows.Thevelocitydistributionsoverthecrosssectionandsecondaryflowinthechannelarealsoexpectedtobealteredduetothepresenceofsuspendedsedimentsintheflow.Forthesereasons,moredispersionisfoundinsediment-ladenflowsthanincorrespondingclear-waterflows.Apredictorforthedispersioncoefficientinsediment-ladenflowsisproposed.

  • 标签: 沉积学 污染物 浓度 污水处理
  • 简介:In1997,theTZ-162wellinTazhongareaoftheTarimbasinhitthelowerPaleozoicdolomitereservoiratadepthof5,900m.Thedistributionofthedolomitereservoir,however,wasverydifficulttodelineateduetothecomplexsurfaceconditionsandpoorseismicproperties.High-precisiontransientelectromagneticsounding(TEM)wasconductedandgoodresultsobtainedinthisarea.Thispaperdiscussedtheprinciple,dataprocessingandinterpretationofthismethod.Theresultsofstudyingthedolomitereservoirsdemonstratedtheeffectivenessofthemethodinstudyingthelow-resistancedolomitereservoirsinthehigh-resistancecarbonates.Thismethodshouldbeaneffectiveonetostudyreservoirsinareaswithsimilarphysicalpropertiesaswell.

  • 标签: 碳酸盐 电磁法 塔里木盆地 古生代
  • 简介:TheCarboniferousandPre-CarboniferousformationsinLudong,Zhungarbasin,containfavorableoil/gasreservoirs.TheCarboniferousformations,however,arecomplexinstructureandexhibitlateralvariationsinlithology.SeismicreflectionsfromPre-Triassicformationsarepoorandthevolcanicreservoirsareverydifficulttoidentify.Theanalysisofphysicalpropertiesconcludedthatthemajortargetsinthisregion,i.e.,thetopoftheJurassicandCarboniferousformations,providedistinctdensityinterfaces.Thebasic,intermediateandacidvolcanicrockswerealsodifferentindensity,resultingindistinguishablegravityanomalies.Thedifferencesinmagnetisminthisregionexistednotonlybetweenthevolcanicrocksandclasticsedimentaryrocksbutalsoamongvolcanicrockswithdifferentcompositions.Allformationsandvolcanicrocksofdifferentlithologiespresentedhighandlowresistanceinterbeds,whicharecharacterizedbyregionaltrends.Themodelingstudydemonstratedthatnon-seismicintegratedgeophysicaltechniquesshouldbefeasibleinthisregion,especiaUythehigh-precisiongravity/magneticmethodscombinedwithlongoffsettransientelectromagneticsounding.

  • 标签: 地球物理学 火山岩 石炭纪 油气蓄积
  • 简介:Upwellingcoastalsystemscanbeusedtounderstandhowdissolvedoxygenandbiologicalproductivitycontroltheaccumulationofredox-sensitivemetalsinmarinesediments.Thealuminium(Al),cadmium(Cd),iron(Fe),nickel(Ni),molybdenum(Mo),vanadium(V),totalorganiccarbon(TOC),totalnitrogen(TN)andtotalsulfur(TS)contentsinsurficialsedimentcollectedfromdifferentwaterdepths(30,70,and120m)inthreenorthernChileanbaysinfluencedbycoastalupwellingandoxygenminimumzones(OMZs)weremeasured.Principalcomponentanalysis(PCA),clusteranalysis,andSpearman'srankcorrelationwereusedtoidentifythemechanismsresponsiblefortheredox-sensitivemetalaccumulation.Thecontentofredox-sensitivemetalsandorganiccomponentsinsedimentincreasedwithincreasingwatercolumndepth,whereaslithogenicmetalsdecreased.IntheMejillonesdelSurandCalderabays,theenrichmentfactorsoftheredox-sensitivemetalsshowedenrichmentforallmetalswithdepth.TheCdandVenrichmentsaremainlytheproductofbiogenicflowtotheseabed,andtheMoandNienrichmentsareduetopreservationunderlowsubsurfaceoxygenconditions.Sulfatereductionisnotanimportantmechanismintheaccumulationofredox-sensitivemetalsinthesedimentofthethreebays.ThePCAshowedthatthebehaviorsoftheredox-sensitivemetalsandorganiccomponentsreflectdifferencesintheeffectsoftheOMZinsedimentalongthecoastofnorthernChile,withamoreintenseOMZinMejillonesdelSurbayandweakerOMZsinCalderaandInglesabays.However,thehighdegreeofenrichmentinredox-sensitivemetalsinCalderaBaycanbeattributedtotheintenseactivityoftheminingindustrynearthebay,asituationthatproducesgeochemicalbehaviorsimilartothatobservedinMejillonesdelSurBay.

  • 标签: Redox sensitive-metals ATACAMA Desert Enrichment factor
  • 简介:Soilsusceptibilitytodetachmentandtransportsub-processesoferosionisgenerallycontroledbytheaggregatebreakdownmechanism.Measuringparticlesizeandaggregationtotheestimateerodibilitypotentialofsoilsisimportantundererosiverainfallconditions.TheAggregateSizeDistribution(ASD)isoneofthemostimportantdeterminantsofsoilstructurealongwithsoilorganicmattercontentfordescribingtheefficiencyofapplied,sustainablemanagementstrategies.Thisstudyaimedtocomparetheperformancesofthreedifferentaggregatesizedistributionmodelstopredictthecharacteristicaggregatesizeparameter(mediandiameter,D50)forerodedsedimentfrominterrillerosionprocessesofRain-SplashTransport(RST)andRaindropImpactedFlowTransport(RIFT).TheASDsof1143collectedsedimentsamplesfromtheRSTandRIFTprocessesweremeasuredandmodeledbytheLog-normal,Fractal,andWeibullapproaches.TheD50value,asacharacteristicparameterforaggregatesizedistributions,derivedfromthecumulativeASDcurvewascomparedforsoilsfromdifferentlandusetypesanddifferentslopeandrainfallintensityconditions.TheperformanceofeachmodelwasevaluatedusingtheMeanSquareError(MSE)andCoefficientofDetermination(R^2).TheWeibullapproachwasthemostaccuratemodelshowingthebestfitwiththelowestMSEvalues(0.0002≤MSE≤0.0048)andhavingthegreatestR2values(0.936≤R^2≤0.998)whencomparedwiththeLog-normalandFractalmodels.Herewith,forsemi-aridlanduseandsoil,specificshapeandscaleparametersfortheWeibulldistribution,therespectiveASDsweresuccessfullyre-generatedformodelingtheerodedsedimentofthesimulatedRSTandRIFTinterillprocesses.

  • 标签: AGGREGATE SIZE distribution Eroded SEDIMENT Log-normal
  • 简介:Researchonin-channelsandminingisimperativeasitmayhaveasignificantimpactonchannelmorphology.Followingthisquesttoquantitativelycomprehendthephenomenon,experimentalstudiesweredonetoinvestigatethedynamiccharacteristicsofthemigrationofaminingpit.Theevaluationofthemigrationrateofaminingpitinaphysicalscalemodelhasfoundariseinthemigrationrateofthepit'supstreamedgewithincreasingdischarge.Awaveletanalysisappliedforanalyzingscale-dependentmigrationofthebedprofileofaminingpitalsorevealedsimilarfindings.Additionally,thewaveletanalysisexaminedthelength-scaledependentmigrationofaminingpitandadecreaseinthemigrationratehasbeenobservedwithanincreaseinthelengthscale.Theplanformofapit(length-to-widthratio)governstheerosionanddepositionprocessesaroundthepit.Bothphysicalandstatisticalapproachesshowanincreaseinthemigrationratewithanincreaseinthelength-to-widthratioofthepit.Anempiricalformulationhasbeendevelopedforcalculatingthemigrationrateoftheupstreamedgeofaminingpitbasedonpitgeometry(length-to-widthratio),averageflowvelocity,andcriticalshearstressofthebedmaterial.Theresultsalsoshowahigherbedloadtransportrateinthechannelsubjectedtominingascomparedtoaplainbedchannel.

  • 标签: SAND MINING MIGRATION Wavelet analysis BED
  • 简介:Determinationofsedimentstabilityinthefieldischallengingbecausebedshearstress(BSS),adeterminingfactorofsedimenterosion,can’teasilybedirectlymeasured.Totacklethischallengeandreliablyassesssedimenterodibilityinafastflowingriver,astandaloneunderwatercamerasystemandanewinsituflume(ISF)weredevelopedandappliedinthisstudy.ThecamerasystemwasusedtorecordsedimentmovementandthenewISFwasusedformeasuringcriticalbottomshearstress(CBSS).Thecameracanbedeployedaloneinwatertorecordvideosortakepictureswithlightemittingdiode(LED)lightingandflexibleschedulesettings.TheISFisbasedontheconceptthattheamountofforceneededtoerodethesameparticleunderdifferentflowconditionsshouldbesimilar.TwohighresolutionAcousticDopplerCurrentProfilers(ADCP)alsoweredeployedinthefieldtocollectvelocity-depthprofileswhichareusedbyconventionalmethodstocalculateBSSwiththelawofthewall.ThesedimenterodibilitywasthenassessedbasedonthecomparisonbetweentheobtainedCBSSandBSSandthenfurtherverifiedwiththerecordedobservationsfromthedeployedcamera.Theresultsrevealthatthewidelyusedconventionalmethodcanproducelargeuncertaintiesandisnotadequatetoprovidemeaningfulconclusionundertheseconditions.

  • 标签: SEDIMENT ERODIBILITY BED SHEAR stress CRITICAL
  • 简介:Theeffectoffullysubmergedbouldersontheflowstructureinchannelshasbeenstudiedbysomeresearchers.However,manynaturalstreamshavebedmaterialwithbouldersthatarenotfullysubmergedunderwater.Inmanynaturalstreams,boulderscoverbetween1%and10%oftheareaofthestreamreach.Theeffectofnon-submergedbouldersonthevelocityprofileandflowcharacteristicsisveryimportantforassessingriverbeddeformation.Theobjectivesofthispaperaretofindthepatternofvelocitydistributionaroundanon-submergedboulderandtocompareitwiththeclassicalstudiesonflowresistanceandReynoldsstressdistributioninopenchannels.Also,byconsideringthevariationintheReynoldsstressdistributionatdifferentlocationsaroundanon-submergedboulder,theeffectofanon-submergedboulderontheestimationofshearvelocityandresistancetoflowhasbeeninvestigated.Resultsindicatesthatinsidethescourholecausedbyanon-submergedboulderinarivervelocitydistributionsareirregular.However,velocitydistributionsareregularoutsidethescourhole.ThepresenceofthebouldercausesaconsiderabledeviationoftheReynoldsshearstressfromtheclassicdistribution,showinganon-specificdistributionwithnegativevalues.TheclassicalmethodsforcalculatingshearvelocityarenotsuitablebecausethesemethodsdonotgivedetailedvelocityandReynoldsstressdistributionsinnaturalriverswithalotofboulders.Thus,theeffectofanon-submergedboulderontheestimationoftheresistancetoflowbyconsideringthevariationsinvelocityandReynoldsstressdistributionsatdifferentlocationsaroundanon-submergedboulderisimportantandneedstobestudiedinanaturalriverinsteadofjustinlaboratoryflumes.ThenegativevaluesinReynoldsstressdistributionaroundaboulderindicatethattheclassicalmethodsareunabletopredictresistancetoflow,andalsoshowstrongturbulenceinsidethescourholewherethecomplexflowconditionspresentambi

  • 标签: Irregular velocity distribution Logarithmic law Non-submerged
  • 简介:MostofthestudiesonArtificialNeuralNetwork(ANN)modelsremainrestrictedtosmallerriversandcatchments.Inthispaper,anattempthasbeenmadetocorrelatevariabilityofsedimentloadswithrainfallandrunoffthroughtheapplicationoftheBackPropagationNeuralNetwork(BPNN)algorithmforalargetropicalriver.ThealgorithmandsimulationaredonethroughMATLABenvironment.Themethodologycomprisedofacollectionofdataonrainfall,waterdischarge,andsedimentdischargefortheNarmadaRiveratvariouslocations(alongwithtimevariables)andapplicationtodevelopathreelayerBPNNmodelforthepredictionofsedimentdischarges.Fortrainingandvalidationpurposesasetof549datapointsforthemonsoon(16June-15November)periodofthreeconsecutiveyears(1996–1998)wasused.Fortestingpurposes,theBPNNmodelwasfurthertrainedusingasetof732datapointsofmonsoonseasonoffouryears(2006–07to2009–10)atninestations.Themodelwastestedbypredictingdailysedimentloadforthemonsoonseasonoftheyear2010–11.ToevaluatetheperformanceoftheBPNNmodel,errorswerecalculatedbycomparingtheactualandpredictedloads.Thevalidationandtestingresultsobtainedatalltheselocationsaretabulatedanddiscussed.Resultsobtainedfromthemodelapplicationarerobustandencouragingnotonlyforthesub-basinsbutalsofortheentirebasin.Theseresultssuggestthattheproposedmodeliscapableofpredictingthedailysedimentloadevenatdownstreamlocations,whichshownonlinearityinthetransportationprocess.Overall,theproposedmodelwithfurthertrainingmightbeusefulinthepredictionofsedimentdischargesforlargeriverbasins.

  • 标签: Artificial NEURAL network BACK propagation Sediment
  • 简介:Sincelocalscouratbridgepiersinriversandestuariesisamajorcauseofbridgefailure,estimationofthemaximumlocalscourdepthisofgreatimportancetohydraulicandcoastalengineers.Althoughnumerousstudiesthatfocusonscour-depthpredictionhavebeendoneandpublished,understandingoftheflowandturbulencecharacteristicsofthehorseshoevortexthatdrivesthescourmechanisminadevelopingscourholestillisimmature.Thisstudyaimstoquantifythedetailedturbulentflowfieldinadevelopingclear-waterscourholeatacircularpierusingParticleImageVelocimetry(PIV).Thedistributionsofvelocityfields,turbulenceintensities,andReynoldsshearstressesofthehorseshoevortexthatforminfrontofthepieratdifferentscourstages(t=0,0.5,1,12,24,and48h)arepresentedinthispaper.Duringscourdevelopment,thehorseshoevortexsystemwasfoundtoevolvefromoneinitiallysmallvortextothreevortices.Thestrengthandsizeofthemainvortexarefoundtoincreasewithincreasingscourdepth.TheregionsofboththemaximumturbulenceintensityandReynoldsshearstressarefoundtoformatalocationupstreamofthemainvortex,wherethelargeturbulenteddieshavethehighestpossibilityofoccurrence.Resultsfromthisstudynotonlyprovidenewinsightintothecomplexflow-sedimentinteractionatbridgepiers,butalsoprovidevaluableexperimentaldatabasesforadvancednumericalsimulations.

  • 标签: SEDIMENT transport SCOUR Bridge PIER PIV
  • 简介:Thispapersummarizesthelatestdevelopments,futureprospects,andproposedcountermeasuresofreservoirsedimentationandchannelscourdownstreamoftheThreeGorgesReservoir(TGR)ontheYangtzeRiverinChina.Threekeyresultshavebeenfound.(1)TheincomingsedimentloadtotheTGRhasbeensignificantlylowerthanexpected.(2)TheaccumulatedvolumeofsedimentdepositionintheTGRissmallerthanexpectedbecausetheoverallsedimentdeliveryratioisrelativelylow,andthedepositioninthenear-damareaoftheTGRisstilldeveloping.(3)RiverbedscourintheriverreachesdownstreamoftheGezhoubaDamisstilloccurringandchannelscourhasextendedtoreachesasfardownstreamastheHukoureach.Significantly,sedimentationoftheTGRislessproblematicthanexpectedsincethestartofoperationoftheTGRontheonehand;ontheotherhand,thepossibleincreasesinsedimentrisksfromdependenceonupstreamsedimentcontrol,depositioninthereservoir,andscouralongmiddleYangtzeRivershouldbepaidmoreattention.(1)SedimenttrappedbydamsbuiltalongtheupperYangtzeRiverandbilliontonsofloosematerialsonunstableslopesproducedbytheWenchuanEarthquakecouldbenewsedimentsourcesfortheupperYangtzeRiver.Moreseriously,possiblereleaseofthissedimentintotheupperYangtzeRiverduetonewearthquakesorextremeclimateeventscouldoverwhelmtheriversystem,andproducecatastrophicconsequences.(2)IncreasingsedimentdepositionintheTGRisharmfultothesafetyandefficiencyofprojectoperationandnavigation.(3)ThedrasticscouralongthemiddleYangtzeRiverhasintensifiedthedown-cuttingoftheriverbedanderosionofrevetment,ithasalreadyledtoincreasingrisktofloodcontrolstructuresandecologicalsafety.ItissuggestedtocontinuetheFieldObservationProgram,toinitiateresearchprogramsandtofocusonrisksofsedimentation.

  • 标签: YANGTZE River Three Gorges RESERVOIR SEDIMENTATION
  • 简介:Therelationbetweenthewaterdischarge(Q)andsuspendedsedimentconcentration(SSC)oftheRiverRamgangaatBareilly,UttarPradesh,intheHimalayas,hasbeenmodeledusingArtificialNeuralNetworks(ANNs).Thecurrentstudyvalidatesthepracticalcapabilityandusefulnessofthistoolforsimulatingcomplexnonlinear,realworld,riversystemprocessesintheHimalayanscenario.ThemodelingapproachisbasedonthetimeseriesdatacollectedfromJanuarytoDecember(2008-2010)forQandSSC.ThreeANNs(T1-T3)withdifferentnetworkconfigurationshavebeendevelopedandtrainedusingtheLevenbergMarquardtBackPropagationAlgorithmintheMatlabroutines.Networkswereoptimizedusingtheenumerationtechnique,and,finally,thebestnetworkisusedtopredicttheSSCvaluesfortheyear2011.ThevaluesthusobtainedthroughtheANNmodelarecomparedwiththeobservedvaluesofSSC.Thecoefficientofdetermination(R2),fortheoptimalnetworkwasfoundtobe0.99.ThestudynotonlyprovidesinsightintoANNmodelingintheHimalayanriverscenario,butitalsofocusesontheimportanceofunderstandingariverbasinandthefactorsthataffecttheSSC,beforeattemptingtomodelit.Despitethetemporalvariationsinthestudyarea,itispossibletomodelandsuccessfullypredicttheSSCvalueswithverysimplisticANNmodels.

  • 标签: ANN Water DISCHARGE Suspended SEDIMENT concentration
  • 简介:Arobustmethodforcharacterizingthemineralogyofsuspendedsedimentincontinentalriversisintroduced.Itencompasses3steps:thefiltrationofafewmillilitersofwater,measurementsofX-rayenergydispersivespectrausingScanningElectronMicroscopy(SEM),androbustmachinelearningtoolsofclassification.ThemethodisappliedtosuspendedparticlescollectedfromvariousAmazonianrivers.Atotalofmorethan204,000particleswereanalyzedbySEM-EDXS(EnergyDispersiveX-raySpectroscopy),i.e.about15,700particlespersamplingstation,whichleadtotheidentificationof15distinctgroupsofmineralogicalphases.ThesizedistributionofparticlescollectedonthefilterswasderivedfromtheSEMmicrographstakeninthebackscatteredelectronimagingmodeandanalyzedwithImageJfreeware.Thedeterminationofthemainmineralogicalgroupscomposingthebulksedimentassociatedwithphysicalparameterssuchasparticlesizedistributionoraspectratioallowsaprecisecharacterizationoftheloadoftheterrigenousparticlesinriversorlakes.InthecaseoftheAmazonianriversinvestigated,theresultsshowthattheidentifiedmineralogiesareconsistentwithpreviousstudiesaswellasbetweenthedifferentsamplescollected.Themethodenabledtheevolutionofgrainsizedistributionfromfinetocoarsematerialtobedescribedinthewatercolumn.Implicationsabouthydrodynamicsortingofmineralparticlesinthewatercolumnarealsobrieflydiscussed.Theproposedmethodappearswellsuitedforintensiveroutinemonitoringofsuspendedsedimentinriversystems.

  • 标签: MINERALOGY SCANNING Electron MICROSCOPY Suspended SEDIMENT
  • 简介:Theattenuationfactororqualityfactor(Q-factororQ)hasbeenusedtomeasuretheenergyattenuationofseismicwavespropagatinginundergroundmedia.ManymethodsareusedtoestimatetheQ-factor.WeproposeamethodtocalculatetheQ-factorbasedontheprestackQ-factorinversionandthegeneralizedS-transform.TheproposedmethodspecifiesastandardprimarywaveletandcalculatesthecumulativeQ-factors;then,itfindstheinterlaminarQ-factorsusingtherelationbetweenQandoffset(QVO)andtheDixformula.TheproposedmethodisalternativetomethodsthatcalculateinterlaminarQ-factorsafterhorizonpicking.Becausethefrequencyspectrumofeachhorizoncanbeextractedcontinuouslyona2Dtime–frequencyspectrum,themethodiscalledthecontinuousspectralratioslope(CSRS)method.ComparedwiththeotherQ-inversionmethods,themethodoffersnearlyeffortlesscomputationsandstability,andhasmathematicalandphysicalsignificance.WeusenumericalmodelingtoverifythefeasibilityofthemethodandapplyittorealdatafromanoilfieldinAhdeb,Iraq.TheresultssuggestthattheresolutionandspatialstabilityoftheQ-profileareoptimalandcontainabundantinterlaminarinformationthatisextremelyhelpfulinmakinglithologyandfluidpredictions.

  • 标签: Quality factor PRESTACK Q estimation generalized
  • 简介:JointPP–PSinversionoffersbetteraccuracyandresolutionthanconventionalP-waveinversion.P-andS-waveelasticmodulideterminedthroughdatainversionsarekeyparametersforreservoirevaluationandfluidcharacterization.Inthispaper,startingwiththeexactZoeppritzequationthatrelatesP-andS-wavemoduli,acoefficientthatdescribesthereflectionsofP-andconvertedwavesisestablished.Thismethodeffectivelyavoidserrorintroducedbyapproximationsorindirectcalculations,thusimprovingtheaccuracyoftheinversionresults.Consideringthattheinversionproblemisill-posedandthattheforwardoperatorisnonlinear,priorconstraintsonthemodelparametersandmodifiedlow-frequencyconstraintsarealsointroducedtotheobjectivefunctiontomaketheproblemmoretractable.Thismodifiedobjectivefunctionissolvedovermanyiterationstocontinuouslyoptimizethebackgroundvaluesofthevelocityratio,whichincreasesthestabilityoftheinversionprocess.TestsofvariousmodelsshowthatthemethodeffectivelyimprovestheaccuracyandstabilityofextractingPandS-wavemodulifromunderdetermineddata.Thismethodcanbeappliedtoprovideinferencesforreservoirexplorationandfluidextraction.

  • 标签: Pre-stack joint PP–PS INVERSION P-and S-WAVE
  • 简介:MostcurrentprestackAVAjointinversionmethodsarebasedontheexactZoeppritzequationanditsvariousapproximations.However,theseequationsonlyreflecttherelationbetweenreflectioncoefficients,incidenceangles,andelasticparametersoneithersideoftheinterface,whichmeansthatwave-propagationeffects,suchassphericalspreading,attenuation,transmissionloss,multiples,andeventmismatchingofP-andS-waves,arenotconsideredandcannotaccuratelydescribethetruepropagationcharacteristicsofseismicwaves.ConventionalAVAinversionmethodsrequirethatthesewave-propagationeffectshavebeenfullycorrectedorattenuatedbeforeinversionbuttheserequirementscanhardlybesatisfiedinpractice.Usingaone-dimensional(1D)earthmodel,thereflectivitymethodcansimulatethefullwavefieldresponseofseismicwaves.Therefore,weproposeanonlinearmulticomponentprestackAVAjointinversionmethodbasedonthevectorizedreflectivitymethod,whichusesafastnondominatedsortinggeneticalgorithm(NSGAII)tooptimizethenonlinearmultiobjectivefunctiontoestimatemultipleparameters,suchasP-wavevelocity,S-wavevelocity,anddensity.Thisapproachisrobustbecauseitcansimultaneouslycopewithmorethanoneobjectivefunctionwithoutintroducingweightcoefficients.Modeltestsprovetheeffectivenessoftheproposedinversionmethod.Basedontheinversionresults,wefindthatthenonlinearprestackAVAjointinversionusingthereflectivitymethodyieldsmoreaccurateinversionresultsthantheinversionbyusingtheexactZoeppritzequationwhenthewave-propagationeffectsoftransmissionlossandinternalmultiplesarenotcompletelycorrected.

  • 标签: REFLECTIVITY method fast nondominated SORTING genetic
  • 简介:Inmarineseismicexploration,ocean-bottomcabletechniquesaccuratelyrecordthemulticomponentseismicwavefield;however,theseismicwavepropagationinfluid–solidmediacannotbesimulatedbyasinglewaveequation.Inaddition,whentheseabedinterfaceisirregular,traditionalfinite-differenceschemescannotsimulatetheseismicwavepropagationacrosstheirregularseabedinterface.Therefore,anacoustic–elasticforwardmodelingandvector-basedP-andS-waveseparationmethodisproposed.Inthismethod,wedividethefluid–solidelasticmediawithirregularinterfaceintoorthogonalgridsandmaptheirregularinterfaceintheCartesiancoordinatessystemintoahorizontalinterfaceinthecurvilinearcoordinatessystemofthecomputationaldomainusingcoordinatestransformation.Theacousticandelasticwaveequationsinthecurvilinearcoordinatessystemareappliedtothefluidandsolidmedium,respectively.Attheirregularinterface,thetwoequationsarecombinedintoanacoustic–elasticequationinthecurvilinearcoordinatessystem.Wenextintroduceafullstaggered-gridschemetoimprovethestabilityofthenumericalsimulation.Thus,separateP-andS-waveequationsinthecurvilinearcoordinatessystemarederivedtorealizetheP-andS-waveseparationmethod.

  • 标签: IRREGULAR SEABED fluid-solid elastic media ocean