汶川地震产生的应变场和位移场
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摘要
2008年5月12日汶川地震明显改变了区域地震的应变场。理解这种应变场的改变对周围断层构造加载进程和区域地震危险性的改变非常重要。本研究以汶川地震的破裂为驱动源,计算了该地震在近处造成的位移场和应变场。结果表明:该地震使得水平位移场断层南端的近乎东向运动逐渐转变为断层北端的东北向运动。震源附近有米级的位移量级。垂直分量与该地震的震源机制一致,西北盘上升、东南盘下降。断层附近的最大剪应变达3.2e-5,并随距断层的距离很快衰减。平均应变显示断层南部和中部主要表现为压缩,北部表现为拉张。
The 12 May 2008 Wenchuan earthquake has changed the regional strain field significantly.It is important to know how such a change affects the tectonic loading processes of the faults and therefore the seismic potential of the region.Utilizing the slip distribution of the Wenchuan earthquake as the driving source we compute the displacement and strain field near the source.Our result shows that the horizontal displacement field progressively rotated from east direction in southern end to northeast direction in the northern end.The magnitude near the source is in the order of meters.The vertical component is consistent with the Wenchuan focal mechanism with uplift in the northwest side and depression in the southeast side.The strain field is presented as mean strain and different strain.The different strain near the source is up to 3.2e-5 and decay rapidly as the distance from the fault.The mean strain shows predominant compression in the south and central part of the fault and extension in the north part.
The 12 May 2008 Wenchuan earthquake has changed the regional strain field significantly.It is important to know how such a change affects the tectonic loading processes of the faults and therefore the seismic potential of the region.Utilizing the slip distribution of the Wenchuan earthquake as the driving source we compute the displacement and strain field near the source.Our result shows that the horizontal displacement field progressively rotated from east direction in southern end to northeast direction in the northern end.The magnitude near the source is in the order of meters.The vertical component is consistent with the Wenchuan focal mechanism with uplift in the northwest side and depression in the southeast side.The strain field is presented as mean strain and different strain.The different strain near the source is up to 3.2e-5 and decay rapidly as the distance from the fault.The mean strain shows predominant compression in the south and central part of the fault and extension in the north part.
引文
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[21]Nishimura N,Yagi Y.2008.Rupture process for May 12,2008 Sichuan earthquake(preliminary result),http://www.geol.tsukuba.ac.jp/~nisimura/20080512/.
[22]Sladen A.2008.Preliminary Result 05/12/2008(Mw 7.9),EastSichuan,http://www.tectonics.caltech.edu/slip_history/2008_e_sichuan/e_sichuan.html
[23]Shen Z K,Sun J,Zhang P,Wan Y,Wang M,Bürgmann R,Zeng Y,Gan W,Liao H,Wang Q.2009.A rare and unusual event:Deformation and slip of the 12 May 2008 Wenchuan earthquake.(submitted to Nature Geoscience).
[24]沈正康,万永革,甘卫军,等.华北地区700年来地壳应力场演化与地震发生研究[J].中国地震,2004,20(3):211-228.
[25]沈正康,万永革,甘卫军,等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究[J].地球物理学报,2003,46(6):786-795.
[26]万永革、沈正康、兰从欣.兰德斯地震断层面及其附近余震产生的位移场研究[J].地震学报,2005,27(2):139-146.
[2]Stein R S.The role of stress transfer in earthquake occurrence[J].Nature,1999,402:605-609.
[3]万永革,吴忠良,周公威,等.几次复杂地震中不同破裂事件之间的“应力触发”问题[J].地震学报,2000,22(6):568-576.
[4]万永革,吴忠良,周公威,等.地震静态应力触发模型的全球检验[J].地震学报,2002,24(3):302-316.
[5]Wan Y G,Wu Z L,Zhou G W.Small stress change triggering a big earthquake:a test of the critical point hypothesis for earthquake[J].Chin Phys Lett,2003,20(9):1452-1455.
[6]Wan Y,Wu Z,Zhou G.Focal mechanism dependence of static stress triggering of earthquakes[J].Tectnophysics,2004,390:235-243.
[7]Robinson R,Zhou S.Stress interactions within the Tangshan,China,earthquake sequence of 1976[J].Bull Seis Soc Amer,2005,95(6):2501-2505.
[8]Deng J,Gurnis M,Kanamori H,Hauksson E.Viscoelastic flow in the lower crust after the 1992 Landers,California,earthquake[J].Science,1998,282:1689-1692.
[9]万永革,沈正康,尚丹.2005年10月巴基斯坦Mw7.6地震对余震的触发研究[J].中国地震,2006,22(3):277-286.
[10]万永革,沈正康,曾跃华,等.青藏高原东北部的库仑应力积累演化对大地震发生的影响[J].地震学报,2007,29(2):115-129.
[11]万永革,沈正康,曾跃华,等.唐山地震序列应力触发的粘弹性力学模型研究[J].地震学报,2008,30(6):581-593.
[12]Parsons T,Ji C,Kirby E.Stress changes from the 2008 Wenchuan earthquake and increased hazard in t h e S i c h u a n b a s i n[J].N a t u r e,2 0 0 8,doi:10.1038/nature07177
[13]Toda S,Lin J,Meghraoui M,Stein R S.12 May 2008 M=7.9 Wenchuan,China,earthquake calculated to increase failure stress and seismicity rate on three major fault systeMS[J].Geophys.Res.Lett,35,L17305,2008,doi:10.1029/2008GL034903.
[14]万永革,沈正康,盛书中,等.2008年汶川大地震在周围断层上产生的库伦破裂应力变化[J].地震学报,2009.已接收.
[15]Chinnery M A.The stress changes that accompany strike-slip faulting[J].Bull Seism Soc Amer,1963,53:921-932.
[16]陈运泰,林邦慧,林中洋,等.根据地面形变的观测研究1966年邢台地震的震源过程[J].地球物理学报,1975,18(3):164-182.
[17]Okada Y.Internal deformation due to shear and tensile faults in a half-space[J].Bull Seism Soc Amer,1992,82:1018-1040.
[18]陈运泰,许力生,张勇,等.2008年5月12日汶川特大地震震源特性分析报告[R/OL],http://www.eq-igp.a-c.cn/汶川地震专题/初步研究与考察结果(一).
[19]王卫民,赵连锋,李娟,等.四川汶川MS8.0级地震震源过程[J].地球物理学报,2008(5):1403-1410.
[20]Ji C,Hayes G.2008.Preliminary result of the May 12,2008 Mw 7.9 eastern Sichuan,China earthquake,http://earthquake.usgs.gov/eqcenter/eqinthenews/2008/us2008ryan/finite_fault.php.
[21]Nishimura N,Yagi Y.2008.Rupture process for May 12,2008 Sichuan earthquake(preliminary result),http://www.geol.tsukuba.ac.jp/~nisimura/20080512/.
[22]Sladen A.2008.Preliminary Result 05/12/2008(Mw 7.9),EastSichuan,http://www.tectonics.caltech.edu/slip_history/2008_e_sichuan/e_sichuan.html
[23]Shen Z K,Sun J,Zhang P,Wan Y,Wang M,Bürgmann R,Zeng Y,Gan W,Liao H,Wang Q.2009.A rare and unusual event:Deformation and slip of the 12 May 2008 Wenchuan earthquake.(submitted to Nature Geoscience).
[24]沈正康,万永革,甘卫军,等.华北地区700年来地壳应力场演化与地震发生研究[J].中国地震,2004,20(3):211-228.
[25]沈正康,万永革,甘卫军,等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究[J].地球物理学报,2003,46(6):786-795.
[26]万永革、沈正康、兰从欣.兰德斯地震断层面及其附近余震产生的位移场研究[J].地震学报,2005,27(2):139-146.
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