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简介：Thispaperpresentsthesurveyandresearchworkoftwoland-seaprofilesintheBohaiSea,China,carriedoutin2010–2011,includingtheseismicsourcesonlandandinthesea,theoceanbottomseismographs(OBS)andtheirrecovery,thecouplingofOBSandtheenvironmentnoiseinseaarea,thedataqualityofOBSs,andtheresultofdataanalysis.WefocusedontheinvestigationofcrustalstructuresrevealedbythetwoNE\EW-trendingjointland-seaprofiles.IncombinationwiththePn-velocitydistributionandgravitymagneticinversionresultsintheNorthChinaCraton,weproposethattheundulationoftheMohointerfaceintheBohaiandsurroundingareasisnotstrong,andthelithosphericthinningismainlycausedbythethinningofitsmantlepart.TheresearchresultindicatesthatobviouslateralvariationsofMohodepthandseismicvelocityappearnearbyallthelarge-scalefaultsinBohaiSea,andthereisevidenceofunderplatingandreformingofthelowercrustbymantlematerialintheBohaiarea.However,geophysicalevidencedoesnotappeartosupportthe"mantleplume"or"delamination"modelfortheNorthChinaCratondestruction.ThecrustalstructureoftheBohaiSearevealed"arelativelynormalcrustandobviouslythinnedmantlelid",localvelocityanomaliesandinstabilityphenomenainthecrust.ThesefeaturesmayrepresentacombinedeffectofNorthChina-YangtzecollisionatanearlystageandtheremoteactionofPacificplatesubductionatalatestage.

简介：AdetailedsurveyofthereefsintheNanshaIslands’seathatareofstrategicimportanceisconducivetotheirfuturedevelopment.Inthisstudy,atotalof50Landsat8operationallandimager(OLI)imageswereusedtoanalyzethegeologicalfeaturesandspectralcharacteristicsoftheNanshareefs.Theexposedislands/sandbanks,reefflatsandsub-tidalreefswereidentifiedwiththenear-infraredband,theredandgreenbands,andtheblueband,respectively.BasedontherelationshipsamongvariouscharacteristicsandbandsillustratedintheOLIimages,themaximumbetween-clustervariancethresholdalgorithm(OTSUmethod)andthemathematicalmorphologywereemployedtoextractcharacteristicparametersofthespatialgeometryofthereefsfromtoptobottom,whichweresubsequentlyoperatedbyaseriesofpost-processingmethodssuchasvectorization,simplificationandtopologicalanalysis.Amongthe132standalonereefsand16atollsthatareidentifiedinthestudy,fourreefshaveyettobenamedintheStandardNamesofVariousIslandsintheSouthChinaSeaandthewebsiteNanshaIslandsOnline(http://www.nansha.org/).Another24onesareexposedtotheatmosphereevenduringhightides.TaipingIslandwithanareaof0.57km~2representsthelargestexposedgeologicalfeature.Thisstudydemonstratedtheapplicabilityofmedium-resolutionsatelliteimagestoderivethecoralreefinformationeffectivelyandthusprovidedinformationfortherelateddepartmentsthatareresponsibletomanagethecoast.Animprovedresolutionofmultispectralbandswiththepanchromaticbandinhigherspatialresolution(15mforOLIimage)isexpectedtoprovideanoptimumsatellitebasedapproachtomapmarinehabitats.