大地测量约束下的阿尔泰山岩石圈流变结构
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摘要
本文根据大地测量数据得到过去50年左右阿尔泰山富蕴区域形变场,破裂带中段的相对位移最大,平均速率达6mm/a,总体上表现为沿断裂的走滑运动特征.该形变场可以用1931年富蕴8级地震的震后黏弹性松弛模型进行模拟,反演得到下地壳黏滞系数为1.6×1019~7.9×1019Pa.s,上地幔黏滞系数为1.6×1018~6.3×1019Pa.s,与华北、Nevada等地区利用震后变形资料推算的黏度基本一致.根据该地区最佳黏弹性分层模型,最近五十年由于岩石圈下部应力松弛引起的地震破裂带两侧最大水平速率约为4mm/a.我们的研究表明:大陆7~8级大震在几十年后仍可能有可观的地表变形,GPS监测得到的现今变形场可能包含震后变形成分.
Regional horizontal deformation in Fuyun Altay in the past 50 years is obtained from geodetic data,the maximum relative displacement is at the middle rupture section with an average relative velocity up to about 6mm/a,manifesting strike slip character on the whole.The regional deformation can be modeled using postseismic viscoelastic relaxation models caused by M8 Fuyun earthquake in 1931,and the best fit lithospheric viscosities are 1.6×10~(19)～7.9×10~(19)Pa\5s for lower crust and 1.6×10~(18)～6.3×10~(19)Pa\5s for the upper mantle,which are consistent with other regions,for example,North China and Nevada.According to the best fit lithospheric rheological model,the maximum horizontal velocity along the rupture in the past 50 years caused by the postseismic viscoelastic relaxation was about 4 mm/a.This study shows that there may be significant surface deformation in the current crust velocity field caused by M7～8 earthquake several decades ago, which can be monitored by modern GPS.
Regional horizontal deformation in Fuyun Altay in the past 50 years is obtained from geodetic data,the maximum relative displacement is at the middle rupture section with an average relative velocity up to about 6mm/a,manifesting strike slip character on the whole.The regional deformation can be modeled using postseismic viscoelastic relaxation models caused by M8 Fuyun earthquake in 1931,and the best fit lithospheric viscosities are 1.6×10~(19)～7.9×10~(19)Pa\5s for lower crust and 1.6×10~(18)～6.3×10~(19)Pa\5s for the upper mantle,which are consistent with other regions,for example,North China and Nevada.According to the best fit lithospheric rheological model,the maximum horizontal velocity along the rupture in the past 50 years caused by the postseismic viscoelastic relaxation was about 4 mm/a.This study shows that there may be significant surface deformation in the current crust velocity field caused by M7～8 earthquake several decades ago, which can be monitored by modern GPS.
引文
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[2]王晓强,谭凯,李杰等.新疆富蕴地区近五十年形变场研究.大地测量与地球动力学,2006,26(3):8~15Wang X Q,Tan K,Li J,et al.Crustal deformation field in Fuyun areaof Xinjiang in past 50 years(in Chinese).Journal of Geodesy andGeodynamics(in Chinese),2006,26(3):8~15
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[5]沈军,李莹甄,汪一鹏等.阿尔泰山活动断裂.地学前缘,2003,10(特刊):132~141Shen J,Li Y Z,Wang Y P,et al.The active faults in Altai Mountains(in Chinese).Earth Science Frontiers,2003,10(Suppl.):132~141
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[7]Marone C J,Scholz C H,Bilham R.On the mechanics of earthquakeafterslip.J.Geophys.Res.,1991,96(B5):8441~8452
[8]Peltzer G,Rosen P,Rogez F.Poro-elastic rebound along the Landers1992 earthquake surface rupture.J.Geophys.Res.,1998,103:30131~30141
[9]Vergnolle M,Pollitz F,Calais E.Constraints on the viscosity ofcontinental crust and mantal from GPS measurements and postseismicdeformation models in western Mongolia.J.Geophys.Res.,2003,108(B10):2502,doi:10.1029/2002JB002374
[10]Pollitz F.Gravitational-viscoelastic postseismic relaxation on a layeredspherical Earth.J.Geophys.Res.,1997,102:17921~17941
[11]谭凯,王琪,王晓强等.震后形变的解析模型和时空分布特征.大地测量与地球动力学,2005,25(4):23~26Tan K,Wang Q,Wang X Q,et al.Analytic models and space-timedistribution of postseismic deformation.Journal of Geodesy andGeodynamics(in Chinese),2005,25(4):23~26
[12]王有学,韩果花,姜枚等.阿尔泰-阿尔金地学断面地壳结构.地球物理学报,2004,47(2):240~249Wang Y X,Han G H,Jiang M,et a1.Crustal stucture along thegeosciences transect from A1tay to A1tun Tagh.Chinese J.Geophys.(in Chinese),2004,47(2):240~249
[13]Draper N R,Smith H.Applied Regression Analysis,2nd Edition.New York:Wiley,1981
[14]Nakiboglu S M,Lambeck K.A reevaluation of the isostatic rebound ofLake Bonneville.J.Geophys.Res.,1983,88:10439~10447
[15]孙荀英,刘激扬,王仁.1976年唐山地震震时和震后变形的模拟.地球物理学报,1994,37(1):45~55Sun X Y,Liu J Y,Wang R.The simulation of coseismic andpostseismic crustal deformation due to Tangshan Earthquake in1976.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1994,37(1):45~55
[16]朱守彪,蔡永恩.利用GPS观测的时间序列资料反演地壳地幔黏性结构.地球物理学报,2OO6,49(3):771~777Zhu S B,Cai Y E.Inversion of viscous properties of crust and mantlefrom the GPS temporal series measurements.Chinese J.Geophys.(inChinese),2006,49(3):771~777
[17]Reilinger R.Evidence for postseismic viscoelastic relaxation followingthe 1959M=7.5 Hebgen Lake,Montana,Earthquake.J.Geophys.Res.,1986,91(B9):9488~9494
[18]Gourmelen N,Amelung F.Postseismic mantle relaxation in theCentral Nevada Seismic Belt.Science,2005,310:1473~1476
[19]Ivins E R.Transient creep of a composite lower crust:2.Apolymineralic basis for rapidly evolving postseismic deformationmodes.J.Geophys.Res.,1996,101:28005~28028
[20]Tapponnier P,Molnar P.Active faulting and Cenozoic tectonics of theTien Shan,Mongolia and Baikal regions.J.Geophys.Res.,1979,84:3425~3459
[2]王晓强,谭凯,李杰等.新疆富蕴地区近五十年形变场研究.大地测量与地球动力学,2006,26(3):8~15Wang X Q,Tan K,Li J,et al.Crustal deformation field in Fuyun areaof Xinjiang in past 50 years(in Chinese).Journal of Geodesy andGeodynamics(in Chinese),2006,26(3):8~15
[3]新疆维吾尔自治区地震局.富蕴地震断裂带.北京:地震出版社,1985Earthquake Administration of Xinjiang Uygur Autonomous Region.The Earthquake Rupture in Fuyun(in Chinese).Beijing:Seismological Press,1985
[4]Wang Q,Zhang P Z,Freymueller J,et al.Present-day crustaldeformation in China constrained by Global Positioning Systemmeasurements.Science,2001,294:574~577
[5]沈军,李莹甄,汪一鹏等.阿尔泰山活动断裂.地学前缘,2003,10(特刊):132~141Shen J,Li Y Z,Wang Y P,et al.The active faults in Altai Mountains(in Chinese).Earth Science Frontiers,2003,10(Suppl.):132~141
[6]Okada Y.Surface deformation due to shear and tensile faults in a half-space.Bulletin of Seismological Society of America,1985,75:1135~1154
[7]Marone C J,Scholz C H,Bilham R.On the mechanics of earthquakeafterslip.J.Geophys.Res.,1991,96(B5):8441~8452
[8]Peltzer G,Rosen P,Rogez F.Poro-elastic rebound along the Landers1992 earthquake surface rupture.J.Geophys.Res.,1998,103:30131~30141
[9]Vergnolle M,Pollitz F,Calais E.Constraints on the viscosity ofcontinental crust and mantal from GPS measurements and postseismicdeformation models in western Mongolia.J.Geophys.Res.,2003,108(B10):2502,doi:10.1029/2002JB002374
[10]Pollitz F.Gravitational-viscoelastic postseismic relaxation on a layeredspherical Earth.J.Geophys.Res.,1997,102:17921~17941
[11]谭凯,王琪,王晓强等.震后形变的解析模型和时空分布特征.大地测量与地球动力学,2005,25(4):23~26Tan K,Wang Q,Wang X Q,et al.Analytic models and space-timedistribution of postseismic deformation.Journal of Geodesy andGeodynamics(in Chinese),2005,25(4):23~26
[12]王有学,韩果花,姜枚等.阿尔泰-阿尔金地学断面地壳结构.地球物理学报,2004,47(2):240~249Wang Y X,Han G H,Jiang M,et a1.Crustal stucture along thegeosciences transect from A1tay to A1tun Tagh.Chinese J.Geophys.(in Chinese),2004,47(2):240~249
[13]Draper N R,Smith H.Applied Regression Analysis,2nd Edition.New York:Wiley,1981
[14]Nakiboglu S M,Lambeck K.A reevaluation of the isostatic rebound ofLake Bonneville.J.Geophys.Res.,1983,88:10439~10447
[15]孙荀英,刘激扬,王仁.1976年唐山地震震时和震后变形的模拟.地球物理学报,1994,37(1):45~55Sun X Y,Liu J Y,Wang R.The simulation of coseismic andpostseismic crustal deformation due to Tangshan Earthquake in1976.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1994,37(1):45~55
[16]朱守彪,蔡永恩.利用GPS观测的时间序列资料反演地壳地幔黏性结构.地球物理学报,2OO6,49(3):771~777Zhu S B,Cai Y E.Inversion of viscous properties of crust and mantlefrom the GPS temporal series measurements.Chinese J.Geophys.(inChinese),2006,49(3):771~777
[17]Reilinger R.Evidence for postseismic viscoelastic relaxation followingthe 1959M=7.5 Hebgen Lake,Montana,Earthquake.J.Geophys.Res.,1986,91(B9):9488~9494
[18]Gourmelen N,Amelung F.Postseismic mantle relaxation in theCentral Nevada Seismic Belt.Science,2005,310:1473~1476
[19]Ivins E R.Transient creep of a composite lower crust:2.Apolymineralic basis for rapidly evolving postseismic deformationmodes.J.Geophys.Res.,1996,101:28005~28028
[20]Tapponnier P,Molnar P.Active faulting and Cenozoic tectonics of theTien Shan,Mongolia and Baikal regions.J.Geophys.Res.,1979,84:3425~3459
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