龙门山断裂带西南段闭锁与变形特征
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摘要
为研究龙门山断裂带西南段断层闭锁程度与变形状态,并分析该区域地震危险性,利用1999—2007、2009—2011、2011—2013和2013—2015年共4期GPS速度场,采用DEFNODE负位错反演程序估算了该断裂的闭锁程度和滑动亏损空间动态分布,并结合1990—2017年跨断层水准资料分析了断层的三维运动变形特征。结果表明:(1)龙门山断裂带西南段在汶川地震前后一直处于较强的闭锁状态,且汶川地震使西南段应变积累速度加快,加速了芦山地震的孕育进程;芦山地震后西南段闭锁程度并没有明显减弱,芦山地震对西南段的应变能释放是局部的和有限的。(2)龙门山断裂带4期垂直断层滑动亏损速率均为挤压亏损速率,汶川地震后西南段亏损速率明显增大,而后2期西南段亏损速率逐渐减小,目前依然明显高于汶川地震前量值。(3)汶川地震前跨断层水准结果显示龙门山断裂带西南段处于完全闭锁状态,汶川地震后多个场地的年均垂直变化速率明显增大,并随时间呈逐渐衰减状态,目前已经恢复至汶川地震前正常变化速率,因此西南段仍然处于闭锁状态。综合GPS反演结果和跨断层水准结果分析认为,目前龙门山断裂带西南段在大部分段落处于强闭锁状态下依然有发生大地震的可能性。
To study the dynamic characteristics of fault locking and deformation,and seismic risk in southwestern segment of the Longmenshan fault,we selected the negative dislocation model of DEFNODE to invert the spatial fault locking and fault slip deficit variations,by using GPS velocity field data during 1999-2007,2009-2011,2011-2013 and 2013-2015. and analyzed the 3-dimensional movement and deformation of the fault combining with the cross fault leveling data during 1990-2017. The results showthat(1) : The Wenchuan earthquake didn't rupture the southwestern segment of the Longmenshan fault,which is always tightly locked.The Wenchuan earthquake accelerated strain accumulation of the southwestern segment and seismogenic process of the Lushan Earthquake. Fault locking of southwestern segment didn't reduce obviously after the Lushan Earthquake. The Lushan earthquake didn't release all the accumulated strain of the southwestern segment which is tightly locked,and the strain releasing was locall and limited.(2) The vertical fault slip deficits during four periods are all compressional. Slip deficit of the southwestern segment increased obviously after the Wenchuan earthquake,and then it decreased gradually. Slip deficit at present is much larger than that before the Wenchuan earthquake.(3) Annual vertical change rate reveals the southwestern segment of the Longmenshan fault is tightly locked before the Wenchuan earthquake. Several field rates increased obviously after the Wenchuan earthquake,then gradually decreased,and returned to normal at present. Combining GPS results and cross fault leveling results,we consider it is possible that major earthquakes happen in southwestern segment under the condition of its most segments tightly locked.
To study the dynamic characteristics of fault locking and deformation,and seismic risk in southwestern segment of the Longmenshan fault,we selected the negative dislocation model of DEFNODE to invert the spatial fault locking and fault slip deficit variations,by using GPS velocity field data during 1999-2007,2009-2011,2011-2013 and 2013-2015. and analyzed the 3-dimensional movement and deformation of the fault combining with the cross fault leveling data during 1990-2017. The results showthat(1) : The Wenchuan earthquake didn't rupture the southwestern segment of the Longmenshan fault,which is always tightly locked.The Wenchuan earthquake accelerated strain accumulation of the southwestern segment and seismogenic process of the Lushan Earthquake. Fault locking of southwestern segment didn't reduce obviously after the Lushan Earthquake. The Lushan earthquake didn't release all the accumulated strain of the southwestern segment which is tightly locked,and the strain releasing was locall and limited.(2) The vertical fault slip deficits during four periods are all compressional. Slip deficit of the southwestern segment increased obviously after the Wenchuan earthquake,and then it decreased gradually. Slip deficit at present is much larger than that before the Wenchuan earthquake.(3) Annual vertical change rate reveals the southwestern segment of the Longmenshan fault is tightly locked before the Wenchuan earthquake. Several field rates increased obviously after the Wenchuan earthquake,then gradually decreased,and returned to normal at present. Combining GPS results and cross fault leveling results,we consider it is possible that major earthquakes happen in southwestern segment under the condition of its most segments tightly locked.
引文
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赵静,江在森,牛安福,等.2017.喜马拉雅主逆冲断层闭锁程度与滑动亏损特征研究[J].武汉大学学报(信息科学版),42(12):1756-1764.
赵静,江在森,武艳强,等.2012.汶川地震前龙门山断裂带闭锁程度和滑动亏损分布研究[J].地球物理学报,55(9):2963-2972.
赵静,牛安福,李强,等.2016.陇西块体周边断层闭锁程度与滑动亏损特征研究[J].地震研究,39(3):351-358.
赵静,武艳强,江在森,等.2013.芦山地震前龙门山断裂带闭锁程度与变形动态特征研究[J].地震学报,35(5):681-691.
周海涛,陈兆辉,朱爽,等.2017.川滇地区部分连续GPS测点形变异常分析[J].地震研究,40(1):94-100.
朱介寿.2008.汶川地震的岩石圈深部结构与动力学背景[J].成都理工大学学报(自然科学版),35(4):348-356.
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Hao M,Wang Q L,Shen Z K,et al.2014.Present day crustal vertical movement inferred from precise leveling data in eastern margin of Tibetan Plateau[J].Tectonophysics,632:281-292.
Mc Caffrey R,Qamar A I,King R W,et al.2007.Fault locking,block rotation and crustal deformation in the Pacific Northwest[J].Geophys JInt,169:1315-1340,doi:10.1111/j.1365-246X.2007.03371.x.
Mc Caffrey R.2002.Crustal block rotations and plate coupling,in Plate Boundary Zones[M].Geodynamics Series,30:101-122.
Meade B J.2007.Present-day kinematics at the India-Asia collision zone[J].Geology,35(1):81-84.
Moreno M,Rosenau M,Oncken O.2010.2010 Maule earthquake slip correlates with pre-seismic locking of Andean subduction zone[J].Nature,467(7312):198-202.
Savage J C,Gan W J,Svarc J L.2001.Strain accumulation and rotation in the eastern California Shear Zone[J].Geophys Res,106(B10):21995-22007.
Schurr B,Asch G,Hainzl S,et al.2014.Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake[J].Nature,512(7514):299-302.
Thatcher W.2007.Microplate model for the present-day deformation of Tibet[J].Journal of Geophysical Research:Solid Earth,112(B1).
Wang Q,Qiao X J,Lan Q G,et al.2011.Rupture of deep faults in the2008 Wenchuan earthquake and uplift of the Longmen Shan[J].Nature Geosci,4:634-640,doi:10.1038/NGEO1210.
Xu X W,Wen X Z,Yu G H,et al.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 MW7.9 Wenchuan earthquake,China[J].Geology,37(6):515-518,doi:10.1130/G25462A.1.
单斌,熊熊,郑勇,等.2009.2008年5月12日MW7.9汶川地震导致的周围断层应力变化[J].中国科学:地球科学,39(5):537-545.
单斌,熊熊,郑勇,等.2013.2013年芦山地震导致的周边断层应力变化及其与2008年汶川地震的关系[J].中国科学:地球科学,43(6):1002-1009.
杜方,闻学泽,张培震,等.2009.2008年汶川8.0级地震前横跨龙门山断裂带的震间形变[J].地球物理学报,52(11):2729-2738.
方颖,江在森,杨永林,等.2010.汶川MS8.0地震前后鲜水河断裂南段的变形特征[J].大地测量与地球动力学,30(3):22-26.
江在森,丁平,王双绪,等.2001.中国西部大地形变监测与地震预报[M].北京:地震出版社.
李媛,刘峡,刘希康,等.2016.2016年门源MS6.4地震前祁连山周边断层活动分析[J].大地测量与地球动力学,36(4):288-293.
乔学军,王琪,杜瑞林.2004.川滇地区活动地块现今地壳形变特征[J].地球物理学报,47(5):805-811.
邵志刚,周龙泉,蒋长胜,等.2010.2008年汶川MS8.0地震对周边断层地震活动的影响[J].地球物理学报,53(8):1784-1795.
申重阳,王琪,吴云,等.2002.川滇菱形块体主要边界运动模型的GPS数据反演分析[J].地球物理学报,45(3):352-451.
孙赫,季灵运,朱良玉,等.2016.新疆于田MS7.3地震同震与震后形变机制研究[J].大地测量与地球动力学,36(12):1052-1055,1068.
谭凯,王琪,王晓强,等.2005.震后形变的解析模型和时空分布特征[J].大地测量与地球动力学,25(4):23-26.
王丽凤,刘杰,赵金贵,等.2013.2011年日本9.0级地震的同震位错以及震后应力松弛过程对中国大陆的影响[J].地震,33(4):238-247.
王卫民,赵连锋,李娟,等.2008.四川汶川8.0级地震震源过程[J].地球物理学报,51(5):1403-1410.
武艳强,江在森,王敏,等.2013.GPS监测的芦山7.0级地震前应变积累及同震位移场初步结果[J].科学通报,58(20):1910-1916.
徐锡伟,闻学泽,韩竹军,等.2013.四川芦山7.0级强震:一次典型的盲逆断层型地震[J].科学通报,58(20):1887-1893.
徐锡伟,闻学泽,叶建青,等.2008.汶川MS8.0地震地表破裂带及其发震构造[J].地震地质,30(3):597-629.
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066-1073.
赵静,江在森,牛安福,等.2017.喜马拉雅主逆冲断层闭锁程度与滑动亏损特征研究[J].武汉大学学报(信息科学版),42(12):1756-1764.
赵静,江在森,武艳强,等.2012.汶川地震前龙门山断裂带闭锁程度和滑动亏损分布研究[J].地球物理学报,55(9):2963-2972.
赵静,牛安福,李强,等.2016.陇西块体周边断层闭锁程度与滑动亏损特征研究[J].地震研究,39(3):351-358.
赵静,武艳强,江在森,等.2013.芦山地震前龙门山断裂带闭锁程度与变形动态特征研究[J].地震学报,35(5):681-691.
周海涛,陈兆辉,朱爽,等.2017.川滇地区部分连续GPS测点形变异常分析[J].地震研究,40(1):94-100.
朱介寿.2008.汶川地震的岩石圈深部结构与动力学背景[J].成都理工大学学报(自然科学版),35(4):348-356.
Gan W J,Zhang P Z,Shen Z K,et al.2007.Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[J].Journal of Geophysical Research:Solid Earth,112(B808416),doi:1029/2005 JB004120.
Hao M,Wang Q L,Shen Z K,et al.2014.Present day crustal vertical movement inferred from precise leveling data in eastern margin of Tibetan Plateau[J].Tectonophysics,632:281-292.
Mc Caffrey R,Qamar A I,King R W,et al.2007.Fault locking,block rotation and crustal deformation in the Pacific Northwest[J].Geophys JInt,169:1315-1340,doi:10.1111/j.1365-246X.2007.03371.x.
Mc Caffrey R.2002.Crustal block rotations and plate coupling,in Plate Boundary Zones[M].Geodynamics Series,30:101-122.
Meade B J.2007.Present-day kinematics at the India-Asia collision zone[J].Geology,35(1):81-84.
Moreno M,Rosenau M,Oncken O.2010.2010 Maule earthquake slip correlates with pre-seismic locking of Andean subduction zone[J].Nature,467(7312):198-202.
Savage J C,Gan W J,Svarc J L.2001.Strain accumulation and rotation in the eastern California Shear Zone[J].Geophys Res,106(B10):21995-22007.
Schurr B,Asch G,Hainzl S,et al.2014.Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake[J].Nature,512(7514):299-302.
Thatcher W.2007.Microplate model for the present-day deformation of Tibet[J].Journal of Geophysical Research:Solid Earth,112(B1).
Wang Q,Qiao X J,Lan Q G,et al.2011.Rupture of deep faults in the2008 Wenchuan earthquake and uplift of the Longmen Shan[J].Nature Geosci,4:634-640,doi:10.1038/NGEO1210.
Xu X W,Wen X Z,Yu G H,et al.2009.Coseismic reverse-and oblique-slip surface faulting generated by the 2008 MW7.9 Wenchuan earthquake,China[J].Geology,37(6):515-518,doi:10.1130/G25462A.1.