昆仑山8.1级地震对青藏高原东北缘地壳水平形变影响的讨论
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摘要
为了从整体上(较大尺度)把握区域应变场的时—空变化势态,并对区域运动场的描述更加逼真,文中在整体无旋转的基础上使用了以提取低频应变信息为主的连续非线性应变模型。根据《中国地壳运动观测网络》位于青藏高原东北缘GPS测站所产生的复测资料(1999—2001—2004),以1999—2001年的运动为基本参考(阶段性形变背景),从2001、2004年两期资料中分离了2001年昆仑山8.1级地震对其产生的主要影响量,结果表明:①昆仑山8.1级地震对青藏高原东北缘产生了比较显著的影响,且位移与形变的方式与背景有很大的差异;②震后的位移分布更加有序,该区西北地区向西偏南向移动,东南地区向北移动;该区最大位移超过15mm;③地震对该区西北地区的影响是能量释放性的,对东南地区的影响是能量积累性的;④震前面应变以收缩为主,震后西北地区为面膨胀(越西越大),东南部为面收缩地区。从整体上看,昆仑山8.1级地震的发生对青藏高原东北缘地区地震活动具有"东增西减"的作用。
In order to grasp the space-time variation tendencies of regional strain field on the whole(in large scale),and describe the regional movement more vividly,the nonlinear continuous strain model focusing on extracting medium-low frequency strain information has been used in the paper.By use of the GPS data(1999—2001—2004) obtained from GPS monitoring stations on the northeastern edge of Qinghai-Tibet block in the Project of "China Crustl Movement Measuring Network".Taking the movement of 1999—2001 as a deformation background,we separate the main influences of Kunlun Mountain MS8.1 earthquake on the deformation from the data of 2001 and 2004,the results show:First,Kunlun Mountain MS8.1 earthquake produce distinct effect to the northeastern edge of Qinghai-Tibet block,the deformation mode is quite different with the background;Second,the displacement field after earthquake is very ordinal,the northwestern area moves to the WS direction,the southeastern area moves to the N direction,the largest amount of displacement in this area exceeds 15 mm.Third,the effect of this earthquake to the northwestern area exhibits an energy-released character,while,the southeastern area exhibits an energy-accumulated character.Fourth,the surface strain before earthquake is mainly contractive,while,after the earthquake,the northwestern area is dominated by expansion,and the southeastern area is contractive.On the whole,the Kunlun Mountain MS8.1 earthquake acts as a role of "increasing earthquake activities in the east and decreasing in the west"on the northeastern edge of Qinghai-Tibet block.
In order to grasp the space-time variation tendencies of regional strain field on the whole(in large scale),and describe the regional movement more vividly,the nonlinear continuous strain model focusing on extracting medium-low frequency strain information has been used in the paper.By use of the GPS data(1999—2001—2004) obtained from GPS monitoring stations on the northeastern edge of Qinghai-Tibet block in the Project of "China Crustl Movement Measuring Network".Taking the movement of 1999—2001 as a deformation background,we separate the main influences of Kunlun Mountain MS8.1 earthquake on the deformation from the data of 2001 and 2004,the results show:First,Kunlun Mountain MS8.1 earthquake produce distinct effect to the northeastern edge of Qinghai-Tibet block,the deformation mode is quite different with the background;Second,the displacement field after earthquake is very ordinal,the northwestern area moves to the WS direction,the southeastern area moves to the N direction,the largest amount of displacement in this area exceeds 15 mm.Third,the effect of this earthquake to the northwestern area exhibits an energy-released character,while,the southeastern area exhibits an energy-accumulated character.Fourth,the surface strain before earthquake is mainly contractive,while,after the earthquake,the northwestern area is dominated by expansion,and the southeastern area is contractive.On the whole,the Kunlun Mountain MS8.1 earthquake acts as a role of "increasing earthquake activities in the east and decreasing in the west"on the northeastern edge of Qinghai-Tibet block.
引文
[1]中国地震局监测预报司.2001年昆仑山口西8.1级大地震.北京:地震出版社,2002:24-34
[2]陈杰,陈玉坤,丁国瑜,等.2001年昆仑山口西MS8.1级地震地表破裂带.第四纪研究,2003,23(6):629-639
[3]乔学军,王琪,杜瑞林,等.昆仑山口西MS8.1级地震的地壳形变特征.大地测量与地球动力学,2002,22(4):6-11
[4]任金卫,王敏.GPS观测的2001年昆仑山口西MS8.1级地震地壳形变.第四纪研究,2005,25(1):34-44
[5]李延兴,李智,张静华,等.中国大陆及周边地区的水平应变场.地球物理学报,2004,47(2):222-231
[6]石耀霖,朱守彪.用GPS位移资料计算应变方法的讨论.大地测量与地球动力学,2006,26(1):1-8
[7]杨国华,江在森,武艳强,等.中国大陆整体无净旋转基准及其应用.大地测量与地球动力学,2005,25(4):6-10
[8]武艳强,江在森,杨国华,等.GPS数据计算应变的误差分析.国际地震动态,2007,7
[9]Savage J C,Weijun Gan and Svarc J L.Strain accumulation and rotation in the eastern California Shear Zone.J.Geophys.Res.2001,106(B10):21995-22007
[10]杨国华,李延兴,韩月萍,等.中国西部地壳现今变形特征及其机制.测绘学报,2002,31(4):292-299
[2]陈杰,陈玉坤,丁国瑜,等.2001年昆仑山口西MS8.1级地震地表破裂带.第四纪研究,2003,23(6):629-639
[3]乔学军,王琪,杜瑞林,等.昆仑山口西MS8.1级地震的地壳形变特征.大地测量与地球动力学,2002,22(4):6-11
[4]任金卫,王敏.GPS观测的2001年昆仑山口西MS8.1级地震地壳形变.第四纪研究,2005,25(1):34-44
[5]李延兴,李智,张静华,等.中国大陆及周边地区的水平应变场.地球物理学报,2004,47(2):222-231
[6]石耀霖,朱守彪.用GPS位移资料计算应变方法的讨论.大地测量与地球动力学,2006,26(1):1-8
[7]杨国华,江在森,武艳强,等.中国大陆整体无净旋转基准及其应用.大地测量与地球动力学,2005,25(4):6-10
[8]武艳强,江在森,杨国华,等.GPS数据计算应变的误差分析.国际地震动态,2007,7
[9]Savage J C,Weijun Gan and Svarc J L.Strain accumulation and rotation in the eastern California Shear Zone.J.Geophys.Res.2001,106(B10):21995-22007
[10]杨国华,李延兴,韩月萍,等.中国西部地壳现今变形特征及其机制.测绘学报,2002,31(4):292-299
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