用H-Kappa方法反演龙门山断裂带及其邻区的莫霍面深度及波速比分布
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摘要
利用龙门山断裂带及其邻近地区地震台站的远震波形记录,采用时间域迭代反褶积技术求取接收函数,并用多次反射波能量扫描求极大值和波形叠加反演的方法(H-Kappa方法)计算出台站下方的莫霍面深度和波速比。结果显示:莫霍面位于扬子地台西缘部分向西侧倾斜缓降,深度在40～48 km变化,地壳平均波速比值为1.81;都江堰、汶川、耿达一带处在龙门山推覆体范围之内的莫霍面起伏变化不大,深度在45 km左右,地壳平均波速比值为1.707 5;龙门山断裂带西侧的松潘—甘孜地块的平均地壳波速比为1.76,莫霍面深度南面部分比北面深约10 km,呈南深北浅状。
Using tele-seismograms from stations in the region along and surrounding the Longmenshan fault zone,we stacked receiver-functions by means of time-domain iterative deconvolution,using a multiply energy scan and wave form modeling inversion method(H-Kappa),further estimated Moho depths beneath each station through the H-Kappa stacking method,and finally derived the distribution of both the Moho depth and the wave-to-velocity ratio(Vp/Vs).The results show: The Moho of Western margin of the Yangtze Station ranges from 40 to 48 km,the wave-to-velocity ratio(Vp/Vs) is 1.81.The Moho boundary under Longmenshan nappe is of little ups and downs around 45 km,the wave-to-velocity ratio(Vp/Vs) is 1.7075.The wave-to-velocity ratio(Vp/Vs) in Songpan-Ganzi block is 1.76.The crustal thickness of southern Songpan-Ganzi block is 10 km thicker than its northern counterpart.
Using tele-seismograms from stations in the region along and surrounding the Longmenshan fault zone,we stacked receiver-functions by means of time-domain iterative deconvolution,using a multiply energy scan and wave form modeling inversion method(H-Kappa),further estimated Moho depths beneath each station through the H-Kappa stacking method,and finally derived the distribution of both the Moho depth and the wave-to-velocity ratio(Vp/Vs).The results show: The Moho of Western margin of the Yangtze Station ranges from 40 to 48 km,the wave-to-velocity ratio(Vp/Vs) is 1.81.The Moho boundary under Longmenshan nappe is of little ups and downs around 45 km,the wave-to-velocity ratio(Vp/Vs) is 1.7075.The wave-to-velocity ratio(Vp/Vs) in Songpan-Ganzi block is 1.76.The crustal thickness of southern Songpan-Ganzi block is 10 km thicker than its northern counterpart.
引文
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[3]KIKUCHI M,KANAMORI H.1982.Inversion of complexbody waves[J].Bull.Seism.Soc.Am.,72:491-50.
[4]王成,朱介寿,宋文杰,等.利用接收函数反龙门山断裂带及邻区深部结构[J].成都理工大学学报(自然科学版)2012,01(1):49-54.
[5]宋文杰.利用被动源地震剖面研究龙门山断裂带及邻区的深部结构[D].成都:成都理工大学,2011.
[6]Christansen N I.Poisson’s ratio and crustal seismology.[J].GeophysRes,1996,101:3139-3156.
[7]楼海,王椿镛,吕智勇,等.2008年汶川MS8.0级地震的深部构造环境——远震P波接收函数和布格重力异常的联合解释[J].中国科学(D辑),2008,38(10):1207-1220.
[8]Christansen N I,Mooney W D.Seismic velocity structureand composition of the continental crust.[J].GeophysRes,1995,100:9716-9788.
[9]朱迎堂,王绪本,余年,等.龙门山大地电磁深部结构及汶川级地震(Ms8.0)[J].地质学报,2008,82(12):1770-1777.
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