利用震后GPS数据反演汶川地区有效黏滞系数
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摘要
利用2009—2011年汶川震区GPS水平速度场数据,综合考虑汶川震后的余滑模型、黏弹性松弛模型及用于描述地壳长期运动的弹性块体模型,采用格网搜索法反演了汶川震区中下地壳的有效黏滞系数.地壳介质黏滞系数不同是造成震后断层两侧地壳水平运动差异的主要因素.研究发现,龙门山断裂带两侧中下地壳介质的黏滞系数差别很大.龙门山断裂以西川西块体中下地壳(16—40km)的有效黏滞系数约为7×1019Pa·s,而龙门山断裂以西、岷江断裂以东的岷江地块中下地壳(16—40km)的有效黏滞系数约为1020Pa·s,比川西地块大.龙门山断裂以东的四川盆地中下地壳(16—40km)的有效黏滞系数约为7×1022Pa·s,比岷江地块和川西地块均大,呈现极强的刚性运动特点.此外,由于同震破裂滑脱面的存在,震中附近的余滑效应比较显著.
Combing with the after-slip model,the viscoelastic relaxation model and the elastic block model,this paper estimates the effective viscosity of middle to lower crust by fitting the observed GPS velocity in Wenchuan region in the period of 2009—2011.The results indicate that the effective viscosity of middle to lower crust in Wenchuan region varies largely for the two sides of Longmenshan fault zone,which impacts the kinematics' patterns of the crust in the study region.The effective viscosity of lower crust is about 7×1019 Pa·s to the western side of Longmenshan fault except the Minjiang block which contains a slightly stronger middle to lower crust;the effective viscosity is about 7×1022 Pa·s to the eastern side of Longmenshan fault,showing a strong rigidmotion characteristics.In addition,the after-slip effect is notable because of the existing coseismic rupture surface.
Combing with the after-slip model,the viscoelastic relaxation model and the elastic block model,this paper estimates the effective viscosity of middle to lower crust by fitting the observed GPS velocity in Wenchuan region in the period of 2009—2011.The results indicate that the effective viscosity of middle to lower crust in Wenchuan region varies largely for the two sides of Longmenshan fault zone,which impacts the kinematics' patterns of the crust in the study region.The effective viscosity of lower crust is about 7×1019 Pa·s to the western side of Longmenshan fault except the Minjiang block which contains a slightly stronger middle to lower crust;the effective viscosity is about 7×1022 Pa·s to the eastern side of Longmenshan fault,showing a strong rigidmotion characteristics.In addition,the after-slip effect is notable because of the existing coseismic rupture surface.
引文
陈运泰.2008.汶川特大地震的震级和断层长度[J].科技导报,26 (10 ):26 --27.Chen Y T.2008.On the magnitude and the fault length of the great Wenchuan earthquake[J].Science and Technology Review,26(10):26--27(in Chinese).
董运洪,罗三明,韩月萍,陈长云.2012.汶川MS8 .0地震北川附近同震和震后垂直位移特征[J].地震学报,34(5):611 --620.Dong Y H,Luo S M,Han Y P,Chen C Y.2012.Co-and post-seismic vertical displacements of Wenchuan MS8.0earthquake near Beichuan[J].Acta Seismologica Sinica,34(5):611--620(in Chinese).
郝明,王庆良,占伟,李煜航.2011.中国东西部地区震后形变有效松弛时间研究[J].大地测量与地球动力学,31(6):49--53.Hao M,Wang Q L,Zhan W,Li Y H.2011.On effective relaxation time of post-seismic deformation in eastern and western China[J].Journal of Geodesy and Geodynamics,31(6):49--53(in Chinese).
蒋锋云,王庆良,朱良玉.2011.汶川地震震前龙门山以西地壳垂直隆升机理分析[J].大地测量与地球动力学,31(5):26 --29.Jiang F Y,Wang Q L,Zhu L Y.2011.Mechanism analysis of vertical uplift of crust in the west of Longmenshan before Wenchuan MS8.0earthquake[J].Journal of Geodesy and Geodynamics,31(5):26--29(in Chinese).
石耀霖,曹建玲.2008.中国大陆岩石圈等效粘滞系数的计算和讨论[J].地学前缘,15(3):82--95.Shi Y L,Cao J L.2008.Effective viscosity of China continental lithosphere[J].Earth Science Frontiers,15(3):82--95(in Chinese).
孙荀英,刘激扬,王仁.1994.1976年唐山地震震时和震后变形的模拟[J].地球物理学报,37(1):45--55.Sun X Y,Liu J Y,Wang R.1994.Simulation of coseismic and postseismic deformation in Tangshan earthquake of 1976[J].Chinese J Geophys,37(1):45--55(in Chinese).
谈洪波,申重阳,李辉,李冀,玄松柏,邢乐林.2009.汶川大地震震后重力变化和形变的黏弹分层模拟[J].地震学报,31 (5):491--505.Tan H B,Shen C Y,Li H,Li J,Xuan S B,Xing L L.2009.Simulation of post-seismic gravity change and deformation of the Wenchuan earthquake based on viscoelastic layered half-space model[J].Acta Seismologica Sinica,31(5):491 --505(in Chinese).
滕吉文,张永谦,阮小敏.2010.汶川8.0级大地震的孕育和发生的深层过程与动力成因探讨[J].国际地震动态,(6):2 .Teng J W,Zhang Y Q,Ruan X M.2010.Deep processes and dynamic responses associated with the Wenchuan MS8.0earthquake of 2008[J].Recent Developments in World Seismology,(6):2(in Chinese).
王敏.2009.基于GPS同震位移场约束反演2008年5·12汶川大地震破裂空间分布[J].地球物理学报,52(10):2519--2526.Wang M.2009.Coseismic slip distribution of the 2008Wenchuan great earthquake constrained using GPS coseismic displacement field[J].Chinese J Geophys,52(10):2519--2526(in Chinese).
王椿镛,Mooney W D,王溪莉,吴建平,楼海,王飞.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24 (1):1--16.Wang C Y,Mooney W D,Wang X L,Wu J P,Lou H,Wang F.2002.3Dvelocity structure of lower crust and upper mantle in Chuan--Dian area[J].Acta Seismologica Sinica,24(1):1--16(in Chinese).
王庆良,巩守文.1997.由1990年共和7.0级地震震后垂直形变求得的地球介质有效弛豫时间和粘滞系数[J].地震学报,19(5):480--486.Wang Q L,Gong S W.1997.Estimating the effective viscosity from the vertical deformation in Gonghe earthquake of1990[J].Acta Seismologica Sinica,19(5):480--486.
王庆良,崔笃信,王文萍,张四新,刘锦文,史旗.2008.川西地区现今垂直地壳运动研究[J].中国科学:D辑,38(5):598 --610.Wang Q L,Cui D X,Wang W P,Zhang S X,Liu J W,Shi Q.2008.Investigating vertical crustal deformation of western Sichuan area present[J].Science in China:Series D,38(5):598--610(in Chinese).
徐锡伟,陈桂华,于贵华,孙鑫喆,谭锡斌,陈立春,孙建宝,陈于高,陈文山,张淑萍,李康.2010.5·12汶川地震地表破裂基本参数的再论证及其构造内涵分析[J].地球物理学报,53(10):2321--2336.Xu X W,Chen G H,Yu G H,Sun X Z,Tan X B,Chen L C,Sun J B,Chen Y G,Chen W S,Zhang S P,Li K.2010.Reevaluation of surface rupture parameters of the 5·12Wenchuan earthquake and its tectonic implication for Tibetan uplift[J].Chinese J Geophys,53(10):2321--2336(in Chinese).
许才军,刘洋,温阳茂.2009.利用GPS资料反演汶川MW7 .9级地震滑动分布[J].测绘学报,38(3):195--201,215.Xun C J,Liu Y,Wen Y M.2009.MW7.9Wenchuan earthquake slip distribution inversion from GPS measurements[J].Acta Geodaetica et Cartographica Sinica,38(3):195--201,215(in Chinese).
杨强,党亚明.2010.利用GPS速度场估算青藏高原地壳韧性层等效粘滞系数分布的研究[J].测绘学报,39(5):497--502 .Yang Q,Dang Y M.2010.A research about effective viscosity of Tibetan Plateau lithosphere viscoelastic ductile layer using GPS velocity fields[J].Acta Geodaetica et Cartographica Sinica,39(5):497--502(in Chinese).
张晁军,曹建玲,石耀霖.2008.从震后形变探讨青藏高原下地壳粘滞系数[J].中国科学:D辑,38(10):1250--1257.Zhang C J,Cao J L,Shi Y L.2008.Exploring viscosity of lower crust from postseismic deformation[J].Science in China:Series D,38(10):1250--1257(in Chinese).
张晁军,石耀霖,马丽.2009.昆仑山大地震震后形变反映的地壳岩石流变特性[J].岩土力学,30(9):2552--2558.Zhang C J,Shi Y L,Ma L.2009.Numerical simulation of crust rheological property reflected by post-seismic deformations of Kunlun large earthquake[J].Rock and Soil Mechanics,30(9):2552--2558(in Chinese).
张培震,闻学泽,徐锡伟,甘卫军,王敏,沈正康,王庆良,黄媛,郑勇,李小军,张竹琪,马胜利,冉勇康,刘启元,丁志峰,吴建平.2009.2008年汶川8.0级特大地震孕育和发生的多单元组合模式[J].科学通报,54(7):944--953.Zhang P Z,Wen X Z,Xu X W,Gan W J,Wang M,Shen Z K,Wang Q L,Huang Y,Zheng Y,Li X J,Zhang Z Q,Ma S L,Ran Y K,Liu Q Y,Ding Z F,Wu J P.2009.2008 Wenchuan 8.0earthquake preparation and occurrence of multi-unit combined mode[J].Chinese Sci Bull,54(7):944--953(in Chinese).
赵珠,范军,郑斯华,长谷川昭,堀内茂木.1997.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,19 (6):615--622.Zhao Z,Fan J,Zheng S H,Hasegawa A,Horiuchi S.1997.Crustal structure and accurate hypocenter determination along the Longmenshan fault[J].Acta Seismologica Sinica,19(6):615--622(in Chinese).
朱守彪,蔡永恩.2006.利用GPS观测的时间序列资料反演地壳地幔粘性结构[J].地球物理学报,49(3):771--777.Zhu S B,Cai Y E.2006.Inversion of viscous properties of crust and mantle from the GPS temporal series measurements[J].Chinese J Geophys,49(3):771--777(in Chinese).
Ji C,Hayes G.2008.Preliminary result of the May 12,2008 MW7.9eastern Sichuan,China earthquake[EB/OL].[2008-10-12].http:∥earthquake.usgs.gov/earthquakes/eqinthenews/2008/us2008ryan/finite_fault.php.
Lorenzo-Martin F,Roth F,Wang R J.2006.Inversion for rheological parameters from post-seismic surface deformation associated with the 1960Valdivia earthquake,Chile[J].Geophys J Int,164(1):75--87.
Shen Z K,Sun J B,Zhang P Z,Wan Y G,Wang M,Bürgmann R,Zeng Y H,Gan W J,Liao H,Wang Q L.2009.Slip maxima at fault junctions and rupturing of barriers during the 2008Wenchuan earthquake[J].Nature Geoscience,2(10):718--724.
Sun W K,Okubo S,Peter V.1996.Global displacements caused by point dislocations in a realistic Earth model[J].J Geophys Res,101(B4):8561--8577.
Wang Q,Qiao X J,Lan Q G,Jeffrey F,Yang S M,Xu C J,Yang Y L,You X Z,Tan K,Chen G.2011.Rupture of deep faults in the 2008Wenchuan earthquake and uplift of the Longmen Shan[J].Nature Geoscience,4(9):634--640.
Wang R J,Lorenzo-Martin F,Roth F.2006.PSGRN/PSCMP:A new code for calculating co-and post-seismic deformation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Computers&Geosciences,32:527--541.
Wang Y.2001.Heart flow pattern and lateral variations of lithosphere strength in China Mainland:Constraints on active deformation[J].Phys Earth Planet Inter,126(3/4):121--146.
董运洪,罗三明,韩月萍,陈长云.2012.汶川MS8 .0地震北川附近同震和震后垂直位移特征[J].地震学报,34(5):611 --620.Dong Y H,Luo S M,Han Y P,Chen C Y.2012.Co-and post-seismic vertical displacements of Wenchuan MS8.0earthquake near Beichuan[J].Acta Seismologica Sinica,34(5):611--620(in Chinese).
郝明,王庆良,占伟,李煜航.2011.中国东西部地区震后形变有效松弛时间研究[J].大地测量与地球动力学,31(6):49--53.Hao M,Wang Q L,Zhan W,Li Y H.2011.On effective relaxation time of post-seismic deformation in eastern and western China[J].Journal of Geodesy and Geodynamics,31(6):49--53(in Chinese).
蒋锋云,王庆良,朱良玉.2011.汶川地震震前龙门山以西地壳垂直隆升机理分析[J].大地测量与地球动力学,31(5):26 --29.Jiang F Y,Wang Q L,Zhu L Y.2011.Mechanism analysis of vertical uplift of crust in the west of Longmenshan before Wenchuan MS8.0earthquake[J].Journal of Geodesy and Geodynamics,31(5):26--29(in Chinese).
石耀霖,曹建玲.2008.中国大陆岩石圈等效粘滞系数的计算和讨论[J].地学前缘,15(3):82--95.Shi Y L,Cao J L.2008.Effective viscosity of China continental lithosphere[J].Earth Science Frontiers,15(3):82--95(in Chinese).
孙荀英,刘激扬,王仁.1994.1976年唐山地震震时和震后变形的模拟[J].地球物理学报,37(1):45--55.Sun X Y,Liu J Y,Wang R.1994.Simulation of coseismic and postseismic deformation in Tangshan earthquake of 1976[J].Chinese J Geophys,37(1):45--55(in Chinese).
谈洪波,申重阳,李辉,李冀,玄松柏,邢乐林.2009.汶川大地震震后重力变化和形变的黏弹分层模拟[J].地震学报,31 (5):491--505.Tan H B,Shen C Y,Li H,Li J,Xuan S B,Xing L L.2009.Simulation of post-seismic gravity change and deformation of the Wenchuan earthquake based on viscoelastic layered half-space model[J].Acta Seismologica Sinica,31(5):491 --505(in Chinese).
滕吉文,张永谦,阮小敏.2010.汶川8.0级大地震的孕育和发生的深层过程与动力成因探讨[J].国际地震动态,(6):2 .Teng J W,Zhang Y Q,Ruan X M.2010.Deep processes and dynamic responses associated with the Wenchuan MS8.0earthquake of 2008[J].Recent Developments in World Seismology,(6):2(in Chinese).
王敏.2009.基于GPS同震位移场约束反演2008年5·12汶川大地震破裂空间分布[J].地球物理学报,52(10):2519--2526.Wang M.2009.Coseismic slip distribution of the 2008Wenchuan great earthquake constrained using GPS coseismic displacement field[J].Chinese J Geophys,52(10):2519--2526(in Chinese).
王椿镛,Mooney W D,王溪莉,吴建平,楼海,王飞.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24 (1):1--16.Wang C Y,Mooney W D,Wang X L,Wu J P,Lou H,Wang F.2002.3Dvelocity structure of lower crust and upper mantle in Chuan--Dian area[J].Acta Seismologica Sinica,24(1):1--16(in Chinese).
王庆良,巩守文.1997.由1990年共和7.0级地震震后垂直形变求得的地球介质有效弛豫时间和粘滞系数[J].地震学报,19(5):480--486.Wang Q L,Gong S W.1997.Estimating the effective viscosity from the vertical deformation in Gonghe earthquake of1990[J].Acta Seismologica Sinica,19(5):480--486.
王庆良,崔笃信,王文萍,张四新,刘锦文,史旗.2008.川西地区现今垂直地壳运动研究[J].中国科学:D辑,38(5):598 --610.Wang Q L,Cui D X,Wang W P,Zhang S X,Liu J W,Shi Q.2008.Investigating vertical crustal deformation of western Sichuan area present[J].Science in China:Series D,38(5):598--610(in Chinese).
徐锡伟,陈桂华,于贵华,孙鑫喆,谭锡斌,陈立春,孙建宝,陈于高,陈文山,张淑萍,李康.2010.5·12汶川地震地表破裂基本参数的再论证及其构造内涵分析[J].地球物理学报,53(10):2321--2336.Xu X W,Chen G H,Yu G H,Sun X Z,Tan X B,Chen L C,Sun J B,Chen Y G,Chen W S,Zhang S P,Li K.2010.Reevaluation of surface rupture parameters of the 5·12Wenchuan earthquake and its tectonic implication for Tibetan uplift[J].Chinese J Geophys,53(10):2321--2336(in Chinese).
许才军,刘洋,温阳茂.2009.利用GPS资料反演汶川MW7 .9级地震滑动分布[J].测绘学报,38(3):195--201,215.Xun C J,Liu Y,Wen Y M.2009.MW7.9Wenchuan earthquake slip distribution inversion from GPS measurements[J].Acta Geodaetica et Cartographica Sinica,38(3):195--201,215(in Chinese).
杨强,党亚明.2010.利用GPS速度场估算青藏高原地壳韧性层等效粘滞系数分布的研究[J].测绘学报,39(5):497--502 .Yang Q,Dang Y M.2010.A research about effective viscosity of Tibetan Plateau lithosphere viscoelastic ductile layer using GPS velocity fields[J].Acta Geodaetica et Cartographica Sinica,39(5):497--502(in Chinese).
张晁军,曹建玲,石耀霖.2008.从震后形变探讨青藏高原下地壳粘滞系数[J].中国科学:D辑,38(10):1250--1257.Zhang C J,Cao J L,Shi Y L.2008.Exploring viscosity of lower crust from postseismic deformation[J].Science in China:Series D,38(10):1250--1257(in Chinese).
张晁军,石耀霖,马丽.2009.昆仑山大地震震后形变反映的地壳岩石流变特性[J].岩土力学,30(9):2552--2558.Zhang C J,Shi Y L,Ma L.2009.Numerical simulation of crust rheological property reflected by post-seismic deformations of Kunlun large earthquake[J].Rock and Soil Mechanics,30(9):2552--2558(in Chinese).
张培震,闻学泽,徐锡伟,甘卫军,王敏,沈正康,王庆良,黄媛,郑勇,李小军,张竹琪,马胜利,冉勇康,刘启元,丁志峰,吴建平.2009.2008年汶川8.0级特大地震孕育和发生的多单元组合模式[J].科学通报,54(7):944--953.Zhang P Z,Wen X Z,Xu X W,Gan W J,Wang M,Shen Z K,Wang Q L,Huang Y,Zheng Y,Li X J,Zhang Z Q,Ma S L,Ran Y K,Liu Q Y,Ding Z F,Wu J P.2009.2008 Wenchuan 8.0earthquake preparation and occurrence of multi-unit combined mode[J].Chinese Sci Bull,54(7):944--953(in Chinese).
赵珠,范军,郑斯华,长谷川昭,堀内茂木.1997.龙门山断裂带地壳速度结构和震源位置的精确修订[J].地震学报,19 (6):615--622.Zhao Z,Fan J,Zheng S H,Hasegawa A,Horiuchi S.1997.Crustal structure and accurate hypocenter determination along the Longmenshan fault[J].Acta Seismologica Sinica,19(6):615--622(in Chinese).
朱守彪,蔡永恩.2006.利用GPS观测的时间序列资料反演地壳地幔粘性结构[J].地球物理学报,49(3):771--777.Zhu S B,Cai Y E.2006.Inversion of viscous properties of crust and mantle from the GPS temporal series measurements[J].Chinese J Geophys,49(3):771--777(in Chinese).
Ji C,Hayes G.2008.Preliminary result of the May 12,2008 MW7.9eastern Sichuan,China earthquake[EB/OL].[2008-10-12].http:∥earthquake.usgs.gov/earthquakes/eqinthenews/2008/us2008ryan/finite_fault.php.
Lorenzo-Martin F,Roth F,Wang R J.2006.Inversion for rheological parameters from post-seismic surface deformation associated with the 1960Valdivia earthquake,Chile[J].Geophys J Int,164(1):75--87.
Shen Z K,Sun J B,Zhang P Z,Wan Y G,Wang M,Bürgmann R,Zeng Y H,Gan W J,Liao H,Wang Q L.2009.Slip maxima at fault junctions and rupturing of barriers during the 2008Wenchuan earthquake[J].Nature Geoscience,2(10):718--724.
Sun W K,Okubo S,Peter V.1996.Global displacements caused by point dislocations in a realistic Earth model[J].J Geophys Res,101(B4):8561--8577.
Wang Q,Qiao X J,Lan Q G,Jeffrey F,Yang S M,Xu C J,Yang Y L,You X Z,Tan K,Chen G.2011.Rupture of deep faults in the 2008Wenchuan earthquake and uplift of the Longmen Shan[J].Nature Geoscience,4(9):634--640.
Wang R J,Lorenzo-Martin F,Roth F.2006.PSGRN/PSCMP:A new code for calculating co-and post-seismic deformation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Computers&Geosciences,32:527--541.
Wang Y.2001.Heart flow pattern and lateral variations of lithosphere strength in China Mainland:Constraints on active deformation[J].Phys Earth Planet Inter,126(3/4):121--146.