简介：IntroductionShort-to-imminentprecursorsstillarethemainbasisforearthquakepredictioninthepresenttime.Strongquakes,especiallythosewithnoforeshocks,canbeforecastedtosomeextentbasedonabundantshoat-to-imminentprecursorsandcombiningwiththemid-to-longtermvar...

简介：SeismicityoftheEarth(MC4.5)wascompiledfromNEIC,IRISandISCcataloguesandusedtocomputeb-valuebasedonvarioustimewindows.Itisfoundthatcontinuouscyclicb-variationsoccuronbothlongandshorttimescales,thelatterbeingofmuchhighervalueandsometimesinexcessof0.7oftheabsoluteb-value.Thesevariationsoccurnotonlyyearlyormonthly,butalsodaily.Beforetheoccurrenceoflargeearthquakes,b-valuesstartincreasingwithvariablegradientsthatareaffectedbyforeshocks.Insomecases,thegradientisreducedtozeroortoanegativevalueafewdaysbeforetheearthquakeoccurrence.Ingeneral,calculatedb-valuesattainmaxima1daybeforelargeearthquakesandminimasoonaftertheiroccurrence.Bothlinearregressionandmaximumlikelihoodmethodsgivecorrelatable,butvariableresults.Itisfoundthatanexpandingtimewindowtechniquefromafixedstartingpointismoreeffectiveinthestudyofb-variations.Thecalculatedb-variationsforthewholeEarth,itshemispheres,quadrantsandtheepicentralregionsofsomelargeearthquakesareofbothlocalandregionalcharacter,whichmayindicatethatinsuchcases,thegeodynamicprocessesactingwithinacertainregionhaveamuchregionaleffectwithintheEarth.Theb-variationshavelongbeenknowntovarywithanumberoflocalandregionalfactorsincludingtectonicstresses.Theresultsreportedhereindicatethatgeotectonicstressremainsthemostsignificantfactorthatcontrolsb-variations.ItisfoundthatforearthquakeswithMwC7,anincreaseofabout0.20intheb-valueimpliesastressincreasethatwillresultinanearthquakewithamagnitudeoneunithigher.

简介：

简介：Ｒｅｓｅａｒｃｈｏｎｔｅｍｐｏｒａｌａｎｄｓｐａｔｉａｌｄｉｓｔｒｉｂｕ┐ｔｉｏｎ，ｅｖｏｌｕｔｉｏｎａｒｙｃｈａｒａｃｔｅｒａｎｄｍｅｃｈａｎｉｓｍｏｆｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｆｉｅｌｄｂｅｆｏｒｅａｎｄａｆｔｅｒｔｈｅＴａｎｇｓｈａｎ...

简介：Ｏｎｔｈｅｐｈｙｓｉｃａｌｍｏｄｅｌｏｆｅａｒｔｈｑｕａｋｅｐｒｅｃｕｒｓｏｒｆｉｅｌｄｓａｎｄｔｈｅｍｅｃｈａｎｉｓｍｏｆｐｒｅｃｕｒｓｏｒｓ＇ｔｉｍｅｓｐａｃｅｄｉｓｔｒｉｂｕｔｉｏｎ──ｏｒｉｇｉｎａｎｄｅｖｉｄｅｎｃｅｓｏｆ　ｔｈｅｓｔｒｏｎ...

简介：Itisknownthatstructuralstiffnessandstrengthdistributionshaveanimportantroleintheseismicresponseofbuildings.Theeffectofusingdifferentcode-specifiedlateralloadpatternsontheseismicperformanceoffixed-basebuildingshasbeeninvestigatedbyresearchersduringthepasttwodecades.However,noinvestigationhasyetbeencarriedoutforthecaseofsoil-structuresystems.Inthepresentstudy,throughintensiveparametricanalysesof21,600linearandnonlinearMDOFsystemsandconsideringfivedifferentshearstrengthandstiffnessdistributionpatterns,includingthreecode-specifiedpatternsaswellasuniformandconcentricpatternssubjectedtoagroupofearthquakesrecordedonalluviumandsoftsoils,theeffectofstructuralcharacteristicsdistributiononthestrengthdemandandductilityreductionfactorofMDOFfixed-baseandsoil-structuresystemsareparametricallyinvestigated.Theresultsofthisstudyshowthatdependingonthelevelofinelasticity,soilflexibilityandnumberofdegrees-of-freedoms(DOFs),structuralcharacteristicsdistributioncansignificantlyaffectthestrengthdemandandductilityreductionfactorofMDOFsystems.Itisalsofoundthatathighlevelsofinelasticity,theductilityreductionfactoroflow-riseMDOFsoil-structuresystemscouldbesignificantlylessthanthatoffixed-basestructuresandthereductionislesspronouncedasthenumberofstoriesincreases.

简介：Athree-dimensionalcrustaldensitymodelbeneathNorthChinaisdeterminedusingP-wavetraveltimesandgravitydatumbysequentialinversionmethodinthispaper.Toimprovetheuniquenessofthesolution,weusedalinearrelationshipbetweenvelocityanddensitytoachievemutualconversionsandconstraintsbetweenvelocitydifferenceanddensitydifference.Algebraicreconstructiontechnique(ART)wasusedindensityinversion,whichhighlyimprovedthecalculationspeedcomparingwithcommonleastsquaresmethod.TheinversionresultsindicatethatthecrustaldensitybeneathNorthChinaisextremelyinhomogeneouswithitsdistributioncoherentwithregionaltectonics.ThelowercrustofTaihangmountaintectoniczoneshowsanobviouslowdensitycharacteristic.Weproposedthatitmaybeanindicatorofupwellingofmantlematerialsorpartialmeltingoflowermostcrust.

简介：Inviewofthecorrelationbetweentectonicactivityandseismicity,thestrongearthquakeriskintheNorth-SouthSeismicBeltarousedwideconcernafterthe2014YutianM_S7.3earthquake.UsingtheseismiccatalogoftheChinaEarthquakeNetworksCenter,theBenioffstrainratiointheNorth-SouthSeismicBeltiscalculatedin30daysbeforeandaftertheMarch21,2008andFebruary12,2014YutianM_S7.3earthquakes.Resultsshowthatinayearafterthe2008YutianM_S7.3earthquake,M>5.0earthquakesalloccurrednearthehighstrainratioareaorthejunctionbetweenthelowandhighstrainratioareas,theactivityofstrongearthquakesobviouslycoincideswiththehighstrainratioarea,whichindicatesthattheseareashaveahigherstresslevel.TheYutianearthquakespromotedthereleaseofsmallearthquakesinthehighstressareas.Thisresearchisofcertainindicatingsignificancetothestudyofsubsequentstrongearthquakesofthisregion.

简介：Analysisofdeformationdatameasuredacrossthefaults,regionalverticaldeformationdataandGPSmeasurementsintheSichuan-Yunnanregionmadesincethe1980spermittedustoconcludethatthecrustaldeformationintheregionduringthisperiodoftimewasrelativelyweakandcausedtheoccurrenceofearthquakes(Ms≥6.0),whichwerenotdistributedalongthemajorboundaryactivefaultsintheregionafterthe1981DawuMs6.9earthquakeandthattheseismicactivityischaracterizedbyquasi-clockwisemigration.Thus,itfollowsthatearthquakepredictionresearchshouldbefocusedonthecentralpartoftheSichuan-Yunnanregioninthecomingyears.Finally,aconceptoftemporaldivisionoftheregionintoactiveblocksissuggestedandthepreliminaryresultofthedivisionisgiveninthepaper.

简介：Ｏｎｔｈｅｐｈｙｓｉｃａｌｍｏｄｅｌｏｆｅａｒｔｈｑｕａｋｅｐｒｅｃｕｒｓｏｒｆｉｅｌｄｓａｎｄｔｈｅｍｅｃｈａｎｉｓｍｏｆｐｒｅｃｕｒｓｏｒｓ＇ｔｉｍｅｓｐａｃｅｄｉｓｔｒｉｂｕｔｉｏｎ（Ⅲ）──ａｎｏｍａｌｉｅｓｏｆｓｅｉｓｍｉｃｉｔｙａｎｄｃｒ...

简介：Basedonthemodelsofnon-uniformearthquakedistributioninthepotentialsource,theseismiczonationofWesternPanzhihuaandCentralandSouthernShanxiProvinceisstudied.Theresultsshowthattheusualuniformdistributionmodelmayunderestimatetheseismicriskandresultinareductionoftheareasofhighintensity.Theinfluenceofeachnon-uniformprobabilisticdistributionmethodontheresultofseismiczoningisdiscussed.