In this paper,218 long period Rayleigh wave records from 7 seismic station of CDSN are selected.We applied a partitioned waveform inversion to these data in order to construct a 3\|D model of shear velocity down to 40...In this paper,218 long period Rayleigh wave records from 7 seismic station of CDSN are selected.We applied a partitioned waveform inversion to these data in order to construct a 3\|D model of shear velocity down to 400km depth in the crust and upper mantle of Qinghai\|Tibet plateau and Its Adjacent Regions (22°～44°N,70°～110°E).The first step of the waveform inversion used involved the matching of the waveforms of fundamental and highermost Ravleigh waves with waveforms synthesized from stratified models;in the second stage,the 3\|D model was constructed by solve linear constrains equation. The major structural features inferred from the surface waveform inversions can be summarized as follows:(1) There is a great contrast between surface waveform through Qinghai—Thibet plateau and the others.Main frequency of the former is lower than the latter, which indicate the crust depth of Qinghai—Tibet plateau is deeper than the others. In addition,the amplitude of about 30s period and 50s period is lower than both sides,which implied these exist lower velocity layer at about 25km depth and about 50km depth in Qinghai—Tibet plateau Crust.The former is common,the latter was argued because resolution of most method can not prove it.展开更多
基于1137个钻孔资料的场地模型及相应的土层地震反应分析计算结果,从场地地震动峰值加速度和特征周期两方面讨论分析了中国《建筑抗震设计规范:GB50011—2016》和美国规范IBC(International Building Code)中的场地分类方法。依据场地...基于1137个钻孔资料的场地模型及相应的土层地震反应分析计算结果,从场地地震动峰值加速度和特征周期两方面讨论分析了中国《建筑抗震设计规范:GB50011—2016》和美国规范IBC(International Building Code)中的场地分类方法。依据场地效应一致性分析得出:在中硬土场地上,美国的C类场地的离散性最小;在中软土场地上,中国的Ⅲ类场地表现出一定的弱势性;在软弱土场地上,中国的Ⅳ类场地优势性明显。总体上中国的双指标分类方法体现了一定的优势性。因此,提出了新的场地分类方法,方法中按照覆盖层厚度和30 m两者较小值的土层计算等效剪切波速,并将目前的Ⅱ类场地划分为Ⅱ1和Ⅱ2,将Ⅲ类场地中覆盖层厚度大于50 m且等效剪切波速小于等于170 m/s的场地归类到Ⅳ类场地,500 m/s以下的等效剪切波速分界线提高20 m/s。研究为建立更合理的场地分类方法提供新的解决方案。展开更多
文摘In this paper,218 long period Rayleigh wave records from 7 seismic station of CDSN are selected.We applied a partitioned waveform inversion to these data in order to construct a 3\|D model of shear velocity down to 400km depth in the crust and upper mantle of Qinghai\|Tibet plateau and Its Adjacent Regions (22°～44°N,70°～110°E).The first step of the waveform inversion used involved the matching of the waveforms of fundamental and highermost Ravleigh waves with waveforms synthesized from stratified models;in the second stage,the 3\|D model was constructed by solve linear constrains equation. The major structural features inferred from the surface waveform inversions can be summarized as follows:(1) There is a great contrast between surface waveform through Qinghai—Thibet plateau and the others.Main frequency of the former is lower than the latter, which indicate the crust depth of Qinghai—Tibet plateau is deeper than the others. In addition,the amplitude of about 30s period and 50s period is lower than both sides,which implied these exist lower velocity layer at about 25km depth and about 50km depth in Qinghai—Tibet plateau Crust.The former is common,the latter was argued because resolution of most method can not prove it.
文摘砾性土地震液化风险评价是我国工程防震减灾面临的新问题,原位剪切波速试验是具有普适性的技术手段,但现有方法不适用于中国。建立中国模式下基于剪切波速的砾性土液化概率计算新方法,并与已有的基于地震循环剪应力比CSR(cyclic stress ratio)理论建立的CYY(Cao,Youd and Yuan,简称CYY)计算方法进行对比。采用实测数据和不同概率下液化临界线模型的对比分析表明,所提出的中国模式基于剪切波速的砾性土液化概率计算新方法,解决了CYY方法不适用我国的问题,且模型构造较CYY方法先进,克服了CYY方法难以兼顾不同砾性土层埋深和不同地震动强度的缺点。无论是退化为概率0.5的确定性判别结果,还是实测数据下液化概率计算的可靠性,本方法均优于CYY方法。提出的公式已被具有我国样板规范性质的《建筑工程抗震性态设计通则》修订版采纳,可为相关规范修订及工程应用提供指导与技术支持。
