重力与粘弹性对汶川地震同震及震后变形的影响
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摘要
分别建立弹性与粘弹性的分层半空间模型,利用PSGRN/PSCMP程序,模拟计算汶川地震的同震与震后位移,并与实际GPS观测资料进行了简单对比分析,进而探讨重力及粘度对同震与震后位移的影响.结果显示,低粘度模型对短期内震后位移影响较大,其造成的震后地壳运动接近4mm/yr,甚至超过龙门山断裂带两侧地块间的相对运动速率.因此,其10年尺度的差值能够反映出粘度分层对震后变形的影响,震后由于低粘度的中下地壳、地幔造成的上地壳局部运动不可忽略,这在一定程度上支持龙门山断层下的深部作用过程可能是引发汶川地震的主要因素.
The co-seismic and post-seismc deformations of the Wenchuan Earthquake are calculated with the software PSGRN/PSCMP and compared with the observed GPS data. The differential displacements of the half-space elastic and viscoelastic layering models during time gaps ≤ 10 years illustrate the influence of viscosity on the post-seismic deformation. The lower the viscous crust that is chosen, the higher the postseismic deformation obtained. The crust velocity derived from the lower viscous model is ~4mm/yr, which is faster than the relative motion across the Longmenshan fault according to the GPS observation, and therefore indicates that local movements originating from the low viscous crust and mantle should not be neglected. We conclude that lower viscosity of the lower crust and mantle results in higher postseismic deformation of the upper crust. This conclusion is consistent, to some extent, with several recent studies which suggested that the Wenchuan Earthquake was mainly caused by deep processes beneath the Longmenshan fault.
The co-seismic and post-seismc deformations of the Wenchuan Earthquake are calculated with the software PSGRN/PSCMP and compared with the observed GPS data. The differential displacements of the half-space elastic and viscoelastic layering models during time gaps ≤ 10 years illustrate the influence of viscosity on the post-seismic deformation. The lower the viscous crust that is chosen, the higher the postseismic deformation obtained. The crust velocity derived from the lower viscous model is ~4mm/yr, which is faster than the relative motion across the Longmenshan fault according to the GPS observation, and therefore indicates that local movements originating from the low viscous crust and mantle should not be neglected. We conclude that lower viscosity of the lower crust and mantle results in higher postseismic deformation of the upper crust. This conclusion is consistent, to some extent, with several recent studies which suggested that the Wenchuan Earthquake was mainly caused by deep processes beneath the Longmenshan fault.
引文
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[3]朱介寿.成都理工大学学报(自然科学版),2008,35:348[Zhu J S.J.Chengdu Uni.Tech.(Science and Technology edi-tion),2008,35:348(in Chinese)]
[4]张培震,徐锡伟,闻学泽等.地球物理学报,2008,51:1066[Zhang P Z,Xu X W,Wen X Zet al.Chinese J.Geophys.,2008,51:1066(in Chinese)]
[5]徐锡伟,闻学泽,陈桂华等.中国科学D辑:地球科学,2008,38:529[Xu X W,Wen X Z,Chen G Het al.Science in China D Series:Earth Science,2008,38:529(in Chinese)]
[6]Burchfiel B C,Royden L H,van de Hilst R Det al.GSA To-day,2008,18(7),doi:10.1130/GSATG18A.1
[7]Ji C,Hayes G.Preliminary result of the May12,2008Mw7.9eastern Sichuan,China earthquake,2008,http://earthquake.usgs.gov/eqcenter/eqinthenews/2008/us2008ryan/finite_fault.php
[8]李勇,周荣军,董顺利等.成都理工大学学报(自然科学版),2008,35:404[Li Y,Zhou R J,Dong S Let al.Chinese J.Geophys.,2008,51:404(in Chinese)]
[9]李勇,周荣军,Densmore A L等.第四纪研究,2006,26:40[Li Y,Zhou R J,Densmore A Let al.Quaternary Science,2006,26:40(in Chinese)]
[10]Densmore A L,Ellis M A,Li Yet al.Tectonics,2007,26,TC4005,doi:10.1029/2006TC001987
[11]Chen Z,Burchfiel B C,Liu Yet al.J.Geophys.Res.,2000,105(B7):16215
[13]Zhang P,Shen Z,Wang Met al.Geology,2004,32:809
[14]Shen Z K,Lu J,Wang Met al.J.Geophys.Res.,2005,110(B11409):1
[15]唐文清,陈智梁,刘宇平等.地质通报,2005,24:1169[Tang W Q,Chen Z L,Liu Y Pet al.Geological Bulletin of China,2005,24:1169(in Chinese)]
[16]唐文清,刘宇平,陈智梁等.山地学报,2007,25:103[TangW Q,Liu Y P,Chen Z Let al.J.Mountain Science,2007,25:103(in Chinese)]
[17]唐文清,刘宇平,陈智梁等.成都理工大学学报(自然科学版),2008,35:81[Tang W Q,Liu Y P,Chen Z Let al.J.Chengdu Uni.Tech.(Science and Technology edition),2008,35:81(in Chinese)]
[18]邓启东,陈社发,赵小麟.地震地质,1994,16:389[Deng Q D,Chen S F,Zhao X L.Seismology and Geology,1994,16:389(in Chinese)]
[19]Wang C Y,Han W B,Wu J Pet al.J.Geophys.Res.,2007,112(B07307):1
[20]嘉世旭,张先康.地球物理学报,2008,51:1431[Jia S X,Zhang X K.Chinese J.Geophys.,2008,51:1431(in Chi-nese)]
[21]郝晓光,胡小刚,许厚泽等.大地测量与地球动力学,2008,28(3):129[Hao X G,Hu X G,Xu HZet al.J.Geodesy and Geodynamics,2008,28(3):129(in Chinese)]
[22]Li S,Mooney W D,Fan J.Tectonophysics,2006,420:239
[23]Cook K L,Royden L H.J.Geophys.Res.,2008,113(B0847):1
[24]熊熊,许厚泽,腾吉文.地壳形变与地震,2001,21(2):1[Xiong X,Xu H Z,Teng J W.Crustal deformation and earth-quake.2001,21(2):1(in Chinese)]
[25]石耀霖,曹建玲.地学前缘,2008,15(3):82[Shi Y L,Cao J L.Earth Science Frontiers,2008,15(3):82(in Chinese)]
[26]张培震,邓启东,张国民等.中国科学(D辑),2003,33(增刊):12[Zhang P Z,Deng Q D,Zhang G Met al.Science in China(Series D),2003,33(a):12(in Chinese)]
[27]Wang R J,Lorenzo-Martin F,Roth F.Computers and Geosci-ences,2006,32:527
[28]袁旭东,汪汉胜,柯小平等.大地测量与地球动力学,2007,27(1):70[Yuan X D,Wang H S,Ke X Pet al.J.Geodesy Geodynamics,2007,27(1):70(in Chinese)]
[29]国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川Ms8.0级地震的同震位移场.中国科学,2008,38:1195
[30]邓志辉,杨主恩,陈桂华等.地震地质,2008,30:355[Deng Z H,Yang Z E,Chen G Het al.Seismology and Geology,2008,30:355]
[31]Ryder I,Parsons B,Wright TJet al.Geophys.J.Int.,2007,169:1009
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