Long aftershock sequences in North China and Central US: implications for hazard assessment in mid-continents

(整期优先)网络出版时间:2014-01-11
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Becauseseismicactivitywithinmid-continentsisusuallymuchlowerthanthatalongplateboundaryzones,evensmallearthquakescancausewidespreadconcerns,especiallywhentheseeventsoccurinthesourceregionsofpreviouslargeearthquakes.However,thesesmallearthquakesmaybejustaftershocksthatcontinuefordecadesorevenlonger.TherecentseismicityintheTangshanregioninNorthChinaislikelyaftershocksofthe1976GreatTangshanearthquake.ThecurrentearthquakesequenceintheNewMadridseismiczoneincentralUnitedStates,whichincludesaclusterofM*7.0eventsin1811–1812andanumberofsimilareventsinthepastmillennium,isbelievedtoresultfromrecentfaultreactivationthatreleasespre-storedstrainenergyinthecrust.Ifso,thisearthquakesequenceissimilartoaftershocksinthattheratesofenergyreleaseshoulddecaywithtimeandthesequenceofearthquakeswilleventuallyend.WeusesimplephysicalanalysisandnumericalsimulationstoshowthatthecurrentsequenceoflargeearthquakesintheNewMadridfaultzoneislikelyendingorhasended.Recognizingthatmid-continentalearthquakeshavelongaftershocksequencesandcomplexspatiotemporaloccurrencesarecriticaltoimprovehazardassessments.