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1、JournalofVolcanologyandGeothermalResearch138(2004)43–76www.elsevier.com/locate/jvolgeoresRockmassstrengthandslopestabilityoftheHilinaslump,Kı¯laueavolcano,Hawai‘iChrisH.Okubo*GeomechanicsRockFractureGroup,DepartmentofGeologicalSciences/172,MackaySchoolofEarthSciencesandEngi
2、neering,UniversityofNevada,Reno,NV,89557-0138,UnitedStatesReceived26August2003;accepted11June2004AbstractStabilityoftheHilinaslump,onthesouthflankofKı¯laueavolcano,Hawai’i,isinvestigatedusingslopestabilityanalysesbasedonrockmassmechanics.TheHilinaslumpisanactiveexampleofthe
3、giantlandslidesthatareobservedaroundsubmarineflanksofoceanislandvolcanoes.Basedonedificetopology,alongwithderivedrockmassstrengthanddeformabilityparameters,slopestabilityanalysespredictthatthegeometriesofpresent-dayfailuresurfacesoftheHilinaslumpareshallow,locatedatlessthan
4、~3.5kmdepthbelowtheuppersurfaceoftheedifice.ThefailuresurfacesatthebaseoftheHilinaslumparepredictedtobestructurallyindependentfromapreviouslyinterpretedsubjacentdetachmentatthecontactbetweentheKı¯laueaedificeandtheoceaniccrust.Basedonthesemodelresults,theHilinaslumpisenvisi
5、onedtorideatopthesouthflankofKı¯laueaasitspreadsseawardalongthisslippingbasaldetachment.Underpresent-dayslopeandsea-levelconfigurations,localhorizontalgroundaccelerationsgreaterthan~0.4–0.6garepredictedtocauseslipalongfailuresurfaceswithinHilinaslump.Therefore,dynamicstress
6、changesduetoslipalongthesubjacentdetachmentmaypotentiallytriggerslipalongfailuresurfacesoftheHilinaslump.Model-derivedstabilityandfailuresurfacegeometriescanaccountforthedistinctobserveddistributionofslipalongspecificHilinafaultsfollowingtheMfa7.91868Ka’uandMs7.21974Kalapan
7、aearthquakes.Further,thespatialdistributionofsouthflankaftershocksNM1.5recordedbetween1950and1976areconsistentwiththepredicteddistributionofpotentialearthquake-inducedslipoftheHilinafaults.D2004ElsevierB.V.Allrightsreserved.Keywords:Kı¯laueavolcano;Hilinaslump;slopestabilit
8、y;geologichazards;rockmechanics1.IntroductionVolcanoslopestabilityhasgainedmuchatt