简介：Hydrocarbonmicro-seepagecancauseoxidationreductionreactionsandproducealteredmineralsinsurfacesedimentsandsoil.Thetypicalalteredmineralsmappingbytheirdiagnosticspectralfeaturesonhyper-spectralimagesisanimportanttoolforthepetroleumexplorationindustry.Inthisstudy,theairbornehyper-spectraldatawereusedtoinvestigatethealteredmineralsinducedbyhydrocarbonmicro-seepagesbyspectralfeaturefitting(SFF)intheloesscoverageareaofXifengOilfield.Theresultsrevealthatthedistributionregionofthealteredmineralsinducedbyhydrocarbonmicro-seepageislargerthantheknownoilfieldexplorationarea.Thepotentialhydrocarbonmicro-seepageregionwasalsorevealedbythedistributionofalteredmineralsbesidestheknownhydrocarbonarea.Afastindexwasproposedbytheabsorptiondepthsofclayandcarbonatemineralsforassessmentofhydrocarbonmicroseepage.Anditgavemuchclearerboundariesforthehydrocarbonmicro-seepageintheloesscoverageareathanthosebythealteredmineralmapping.Inaddition,somefieldsampleswereanalyzedbyX-raydiffraction(XRD)andatomicabsorptionspectrophotometertovalidatetheresults.Withintheextentsofhydrocarbonmicro-seepage,therearelowercontentsofferricironandhighercontentsofcarbonatemineralsinthesesamples.Therefore,itissatisfactorytohavetheairbornehyper-spectraldatatooutlinetheextentsofhydrocarbonmicro-seepageforfurtherhydrocarbonexplorationintheloesscoveragearea.

简介：Ascientifichypothesisisproposedandpreliminarilyverifiedinthispaper:underthedrivingofseepageflows,theremightbeaverticalmigrationoffine-grainedsoilparticlesfrominteriortosurfaceofseabed,whichisdefinedas‘sub-bottomsedimentpumpaction’inthispaper.FieldexperimentswereperformedtwiceontheintertidalflatoftheYellowRiverdeltatostudythisprocessviabothtrappingthepumpedmaterialsandrecordingtheporepressuresinthesubstrate.Experimentalresultsarequiteinterestingaswedidobserveyellowslurrywhichismainlycomposedoffine-grainedsoilparticlesappearingontheseabedsurface;seepagegradientswerealsodetectedintheintertidalflat,undertheactionoftidesandsmallwindwaves.Preliminaryconclusionsarethat‘sedimentpump’occurswhenseepageforceexceedsacertainthreshold:firstly,itisbigenoughtodisconnectthesoilparticlesfromthesoilskeleton;secondly,thedegreeofseabedfluidizationorbioturbationisbigenoughtoprovidepreferredpathsforthedetachedmaterialstomigrateupwards.Thentheywouldbefirstlypumpedfrominteriortothesurfaceofseabedandtheneasilyre-suspendedintooverlyingwatercolumn.Influentialfactorsof‘sedimentpump’aredeterminedashydrodynamics(waveenergy),degreeofconsolidation,indexofbioturbation(permeability)andcontentoffine-grainedmaterials(sedimentaryage).Thisnewperspectiveof‘sedimentpump’mayprovidesomeimplicationsforthemechanisminterpretationofseveraluncleargeologicalphenomenaintheYellowRiverdeltaarea.

简介：BasedonthedigitalwaveformdatarecordedbyXinjiangDigitalSeismicNetworkfortheXinyuan-HejingM_L6.8earthquakesequencesofJune30,2012,thispaperanalyzesthestressdropsofearthquakesequencesandthecorrelationcoefficientsoffocalmechanismssignificantforstrongaftershocks.Firstly,thesourceparametersoftheXinyuan-HejingM_L6.8earthquakesequencesareobtainedbyapplyingthespectrumanalysisandtheBrunessourcemodel.Then,thecorrelationcoefficientsofspectralamplitudesarecalculatedusingthelow-frequencyspectralamplituderecordedbythesamestationforthedifferentevents.Finally,basedontheresultsofthecorrelationcoefficientsofspectralamplitudes,theeventswithsimilarfocalmechanismsaregroupedusingtheclusteringmethod.Theresultsshowthat:(1)Thestressdropvaluesshowasteadytrendintheaftershocksequencecalmperiodandthestressdropvaluesshowarise-fallinstrongaftershocks.(2)Themovingaveragecorrelationcoefficientofamplitudespectrumbeginstospreadafterthemainshock.Itshowsthatthecorrelationdecreasesbetweenthemainshockandtheaftershocksinmechanisms.(3)Theresultsoffocalmechanismgroupsshowthattheearthquakesequencesaremainlystrikeslips.ThestressdistributionofthemainpressureaxisisnearlyNS,whichisthesameasthestructuralstressfield.(4)Themagnitudeandmechanismshowthatthereisanagreementbeforethestrongaftershock,whichshowsthattheregionalstressfieldisenhanced.

简介：Theearthquakestress-dropvaluesoftwosequenceswereaccuratelycalculatedaftertakingawaytheeffectsduetoregionalearthquakeanelasticattenuationandstationsiteresponse,usingwaveformdataandseismicphasedataofsequencesoftheJingguM_S6.6,andLudianM_S6.5earthquakesinYunnan.Theseresultsshowthatthestressdropwithmagnitudeincreaseswithinthescopeofthisstudyofmagnitude.Aftereliminatingtheinfluenceofthemagnitude,theaveragevalueofstress-dropintheJinggusequenceishigherthanthatoftheLudiansequenceatthesamemagnituderange.Thismayberelatedtothestressstateindifferentregions.Intermsofthechangesoftimeandspaceofstress-drop,beforeM_S5.8strongaftershock,thestress-dropis'slowingdown-turningup-keepingahighvalue'afterthemainshock,meanwhile,almostalloftheabnormallyhighstressdropvalueisdistributedaroundtheM_S5.8strongaftershock,showingthatthestressenvironmentintheregionwasincreasingafterthemainshock.AndaftertheM_S5.9strongaftershock,stress-droprapidlydeclinestoarelativelystablestate,meanwhile,thehighvalueofstress-dropisdistributedaroundthestrongaftershock,showingthattheregionaltectonicstressgetsmorefullyrelease,itsstressenvironmentbeginstorapidlydecrease.FortheLudiansequencewithoutastrongaftershockoccurring,theaveragevalueofstressdropislowerthanthatoftheJingguearthquakesequenceatthesamemagnituderange,whileatthesametime,thestress-dropoftheaftershocksequencealmosthasn'tchangedmuch.Inthetimeafterthemainshock,combinedwiththereleasecharacteristicsofthemainenergy,thestressintheregionisexcessivelyreleased,thesubsequentstressintheregiongraduallyreturnstonormal.ThismaybethereasonwhytheactivityofLudianaftershockssignificantlywasweakerandsubsequentlytherewerenostrongaftershocksoccurred.