简介:Itiswidelyknownthattheseismicresponsecharacteristicsofasoilsitedependsheavilyonseveralkeydynamicpropertiesofthesoilstratum,suchaspredominantfrequencyanddampingratio.Awidelyusedmethodforestimatingthepredominantfrequencyofasoilsitebyusingmicrotremorrecords,proposedbyNakamura,isinvestigatedtodetermineitseffectivenessinestimatingthedampingratio.TheauthorsconductedsomemicrotremormeasurementsofsoilsitesinHongKongandfoundthatNakamura'smethodmightalsobeusedtoestimatethedampingratioofasoilsite.DampingratiodatafromseveraltypicalsoilsiteswereobtainedfrombothNakamura'sratiocurvesusingthehalfpowerpointmethodandresonantcolumntests.Regressionanalysisindicatesthatthereisastrongcorrelationbetweenthedampingratiosderivedfromthesetwodifferentapproaches.
简介:PastresearchershaveanticipatedtheoccurrenceofagreatearthquakeinthecentralHimalayasinthenearfuture.ThismaycauseseriousdamageintheKathmanduValley,whichsitsonanancientlakebedzone,withlacustrinesedimentsofmorethan500mdepth.Inthisstudy,thepredominantfrequencyofgroundmotionisevaluatedusingtheHorizontal-to-Vertical(H/V)spectralratiotechniqueandrecordingsofambientnoise.TheresultsoftheH/Vratioshowtwopeaksinabout20percentofthelocations,whicharedistributedmainlyinandaroundthecenterandnorthernpartoftheKathmanduValley.Thepredominantfrequenciesvaryfrom0.5Hzto8.9Hzinthestudyarea,whereasthesecondresonancefrequencyvariesfrom4Hzto6Hzinthecenterandnorthernpartofthevalley.Thisindicatesthatthecenterandnorthernpartofthevalleyhaveawiderangeofresonancefrequencyduetotwolevelsofimpedancecontrastonemaybefromthesurfacelayerandtheothermaybefromthelayerunderneath.ThesetwolevelsofresonanceindicatetheimportanceofconsideringtheeffectsofsurfaceandlowerlayersduringtheplanninganddesigningofinfrastructuresintheKathmanduValley.