摘要
HeavilypopulatedbyBeijingandTianjincities,BohaibasinisaseismicallyactiveCenozoicbasinsufferingfromhugelostbydevastatingearthquakes,suchasTangshanearthquake.Theattenuation(QPandQS)ofthesurficialQuaternarysedimenthasnotbeenstudiedatnaturalseismicfrequency(1-10Hz),whichiscrucialtoearthquakehazardsstudy.Boreholeseismicrecordsofmicroearthquakeprovideusagoodwaytostudythevelocityandattenuationofthesurficialstructure(0-500m).Wefoundthattherearetwopulseswellseparatedwithsimplewaveformsonboreholeseismicrecordsfromthe2006MW4.9Wen'anearthquakesequence.Thenweperformedwaveformmodelingwithgeneralizedraytheory(GRT)toconfirmthatthetwopulsesaredirectwaveandsurfacereflectedwave,andfoundthattheaveragevPandvSofthetop300minthisregionareabout1.8km/sand0.42km/s,leadingtohighvP/vSratioof4.3.Wealsomodeledsurfacere-flectedwavewithpropagatingmatrixmethodtoconstrainQSandthenearsurfacevelocitystructure.OurmodelingindicatesthatQSisatleast30,orprobablyupto100,muchlargerthanthetypicallyassumedextremelylowQ(～10),butconsistentwithQSmodelinginMississippiembayment.Also,thevelocitygradientjustbeneaththefreesurface(0-50m)isverylargeandvelocityincreasesgraduallyatlargerdepth.Ourmodelingdemonstratestheimportanceofboreholeseismicrecordsinresolvingshallowvelocityandattenuationstructure,andhencemayhelpinearthquakehazardsimulation.
出版日期
2009年05月15日（中国期刊网平台首次上网日期，不代表论文的发表时间）
