简介：Characteristicslipandcharacteristicearthquakemodelshavebeenproposedforseveraldecades.Suchmodelshavebeensupportedrecentlybyhigh-resolutionoffsetmeasurements.Thesemodelssuggestthatslipalongafaultrecursviasimilarlysized,largeearthquakes.Theinter-eventstrainaccumulationrate(ratioofearthquakeslipandprecedinginterseismictimeperiod)isusedheretotestthecharacteristicearthquakemodelbylinkingtheslipandtimingofpastearthquakesontheHaiyuanFault.Weaddresshowtheinter-eventstrainaccumulationratevariesovermultipleseismiccyclesbycombiningpaleoearthquakestudieswithhigh-resolutionairbornelightdetectionandranging(LiDAR)datatodocumentthetimingandsizeofpaleoearthquakedisplacementsalongthewesternandmiddlesegmentsoftheHaiyuanFault.Ourobservationsencompass5earthquakecycles.WefindsignificantvariationsovertimeandspacealongtheHaiyuanFault.WeobservethatonthemiddlesegmentoftheHaiyuanFaulttheratesslowdownorincreaseasananticorrelatedfunctionoftheratesofprecedingearthquakes.Here,weproposethattheinter-eventstrainaccumulationratesonthemiddlesegmentoftheHaiyuanFaultareoscillatingbothspatiallyandtemporally.However,alongthewesternsegment,theinter-eventstrainaccumulationrateisbothspatiallyandtemporallysteady,whichisinagreementwithquasi-periodicandslip-predictablemodels.Finally,weproposethatdifferentfaultsegmentswithinasinglefaultzonemaybehaveaccordingtodifferentearthquakemodels.

简介：Thequantitativeinterpretationofgravityanomaliesduetoshallowstructuresneedsseparationbetweenlongwavelengthanomalies(regionalanomalies)andshortwavelengthanomalies(residualanomalies).Theregional-residualfieldseparationcanbecarriedoutusingthepolynomialmethod.Inthiscase,theso-calledregionalfieldofordernistreatedasapolynomialofdegreen.Thepresentstudyshowsthatthedegreenmustvarybetweenasmallestvaluenminandamaximumvaluenmax.Thisarticlepresentsamethodtoprocessgravitydatathatallowsdeterminationofnminandnmaxforagivenstudyarea.WeapplythemethodtogravitydataoftheSouth-WestCameroonzone.Inthischosenstudyarea,wefindthatregionalanomalymapsofordersrangingfrom1to9andresidualanomalymapsofordersrangingfrom1to8canbeusedforsuitableinterpretation.Theanalysesshowthatonemayneedresidualanomalymapsofseveralorderstoperformsatisfactoryquantitativeinterpretationofthedifferentintrusivebodiesfoundinagivenarea.

简介：TheGarouaZoneinNorthCameroon,thesubjectofthisstudy,isknowntohaveundergonetectonicmovementsduringtheCretaceous,butthezone’sstructuraldataremainpoorlyknown.ThisstudyexploitstheBougueranomalytoimproveknowledgeofGarouatectonicsstructures.Inordertocharacterizethesestructures,twomethodsareused:Euler’sdeconvolutionmethodandthemethodofthehorizontalgradientoftheverticalderivative.SuperpositionoftheEuler’ssolutionsmapforindexN=1withthemapfromthehorizontalgradientoftheverticalderivativemethodallowsdeterminationofgravimetriclineaments,interpretedasfaultsoraslinearcontacts,fromwhichwededuceastructuralmapofthestudyarea.Basedonthismap,weidentifysixteenlineaments,ofwhichwecounteightaslinearcontactsandeightasfaults.Amongthefaults,wedenoteoneofdepthbetween4and8km,fivefaultsofdepthrangingbetween8and13km,andtwofaultsofdepthsbetween13and36km.Analysisofthesefaultsshowsthatthesevendeepestfaultsmightpresentanaturalriskinourstudyarea.Forpurposesofcivilprotection,suchdeepfaultsshouldbemonitoredandtakenintoconsiderationintheimplementationoflargepublicworks.Thestructuralmap,establishedhereinfromdataonthein-depthextensionofeachfault,thusincreasesscientificknowledgeintheareathatcanbeusedtositepublicworksinwaysthatreducerisk.

简介：TheX-discontinuity,whichappearsatthedepthofapproximately300km,isanimportantseismicinterfacewithpositivevelocitycontrastsintheuppermantle.Detectingitspresenceandtopographycanbeusefultounderstandphasetransformationsofrelevantmantlemineralsunderthehigh-temperatureandhigh-pressurecircumstanceoftheEarth'sinterior.Inthisstudy,wedetecttheX-discontinuitybeneaththeRyukyusubductionzoneusingfiveintermediate-deptheventsrecordedbythedenseAlaskaRegionalNetwork(AK).TheX-discontinuityissuccessfullyrevealedfromtherobustslantstackingofthesecondarydown-goingandconvertingSdPphases.Fromthedepthdistributionofconversionpoints,wefindthattheX-discontinuity'sdepthrangesbetween269kmand313km,withanaveragedepthof295km.Alltheconversionpointsarelocatedbeneaththedown-dippingsideofthePhilippineSeaslab.Fromenergycomparisonsinvespagramsforobservedandsyntheticseismograms,thestrongconvertedenergyismorelikelyfromathinhigh-velocitylayer,andtheS-wavevelocityjumpsacrosstheX-discontinuityareupto5%to8%withanaverageof6.0%.Accordingtopreviouspetrologicalandseismologicalstudies,theX-discontinuitywedetectedcanbeinterpretedasthephasetransformationofcoesitetostishoviteineclogiticmaterialswithintheoceaniccrust.