简介:ISO9000族标准是国际标准化组织(ISO)颁布的在全世界范围内通用的关于质量管理和质量保证方面的标准,它不是指一个标准,而是一族标准的统称,目前已被80多个国家采用。
简介: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.