GPS资料反映大震前后青藏高原东北缘的水平形变
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摘要
利用1999～2007年和2009～2011年青藏高原东北缘地区水平形变观测与处理结果,分析了汶川、玉树地震前后该区域水平形变场及其变化,得出:(1)1999～2007年水平运动的大小与方向变化明显,但清晰有序,相对运动一般在15mm/a以内,2009～2011年的水平运动轮廓虽然与1999～2007年相似,但变化可辨,主要体现在震源较近的地域;(2)1999～2007年的主压应变优势方向为南东—北西向,有序与一致性较强,值域一般在(±35～38)×10-9/a之内,最大主应变区呈带状分布于祁连构造带上,2009～2011年最大主应变的大小及空间分布则有一定的差别,震中附近最大约为180×10-9/a,但主应变方向与1999～2007年基本保持一致;(3)1999～2007年最大剪切应变率大小的空间分布呈北西向条带状,较大值域的条带为祁连构造带达27×10-9/a,2009～2011年最大剪切应变率的空间状态不同于以前,最大值位于震源及其附近地区接近120×10-9/a,其他区域相对较小;(4)1999～2007年的旋剪形变呈北西向条带左、右旋交替的分布状态;2009～2011年则没有如此清晰,最大值也位于震中及附近地域。总之,震后区域形变场有较大的调整,可能还在继续中。
Based on the GNSS observation data and its processing result from 1999 to 2007 and from 2009 to 2011 in the northeastern edge of Qinghai-Tibetan plateau,we analyzed the horizontal deformation field and its variation before and after Wenchuan M8.0 and Yushu M7.1 earthquakes.The results show as follows:(1)The rate and direction of horizontal movement changed obviously,but it was clear and ordered,its relatively movement was within 15mm/a from 1999 to 2007.Although the movement profile from 2009 to 2011 was similar as before,there was little difference especially in the region near by the epicenters.(2)The principal compressive strain from 1999 to 2007 had more orderliness and consistency.Its value is between ±35×10-9/a and its superior direction is SE-NW.The region of maximal principal compressive strain showed zonal distribution and located in Qilian tectonic zone.The size and space distribution of maximal principal compressive strain from 2009 to 2011 is different,the maximal value of principal compressive strain near by the epicenter is about 180×10-9/a.However,the direction of it remained the same.(3)The space distribution of the maximal shear strain rate from 2009 to 2011 showed a banding distribution along the north-west direction,the more value of bending which lay in Qilian tectonic belt was 27×10-9/a.The spatial shape of the maximal shear strain rate from 2009 to 2011 is different from the result of 1999~2007,the maximum value of the strain rate from 2009 to 2011 which lay in the epicenter and its adjacent region was 120×10-9 /a.The strain rate in the other region is less.(4)The revolving shear deformation from 1999 to 2007 showed bending distribution along North-West direction and was orderly alternate change with left-lateral and dextral.However,the state of revolving shear deformation from 2009 to 2011 was not clear,and there was the maximum value was around epicenter and its adjacent area.In a word,there were major changes of crustal deformation after earthquakes and it might be on still.
Based on the GNSS observation data and its processing result from 1999 to 2007 and from 2009 to 2011 in the northeastern edge of Qinghai-Tibetan plateau,we analyzed the horizontal deformation field and its variation before and after Wenchuan M8.0 and Yushu M7.1 earthquakes.The results show as follows:(1)The rate and direction of horizontal movement changed obviously,but it was clear and ordered,its relatively movement was within 15mm/a from 1999 to 2007.Although the movement profile from 2009 to 2011 was similar as before,there was little difference especially in the region near by the epicenters.(2)The principal compressive strain from 1999 to 2007 had more orderliness and consistency.Its value is between ±35×10-9/a and its superior direction is SE-NW.The region of maximal principal compressive strain showed zonal distribution and located in Qilian tectonic zone.The size and space distribution of maximal principal compressive strain from 2009 to 2011 is different,the maximal value of principal compressive strain near by the epicenter is about 180×10-9/a.However,the direction of it remained the same.(3)The space distribution of the maximal shear strain rate from 2009 to 2011 showed a banding distribution along the north-west direction,the more value of bending which lay in Qilian tectonic belt was 27×10-9/a.The spatial shape of the maximal shear strain rate from 2009 to 2011 is different from the result of 1999~2007,the maximum value of the strain rate from 2009 to 2011 which lay in the epicenter and its adjacent region was 120×10-9 /a.The strain rate in the other region is less.(4)The revolving shear deformation from 1999 to 2007 showed bending distribution along North-West direction and was orderly alternate change with left-lateral and dextral.However,the state of revolving shear deformation from 2009 to 2011 was not clear,and there was the maximum value was around epicenter and its adjacent area.In a word,there were major changes of crustal deformation after earthquakes and it might be on still.
引文
付碧宏,时丕龙,王萍,等.2009.2008年汶川地震断层北川段的几何学与运动学特征及地震地质灾害效应[J].地球物理学报,52(2):485-495.
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江在森,马宗晋,张希.2003.GPS初步结果揭示的中国大陆水平应变场与构造变形[J].地球物理学报,46(3):352-358.
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杨博,张风霜,韩月萍.2011.球面水平应变场无偏差计算与滤波[J].地震研究,34(1):59-66.
杨国华,韩月萍,杨博,等.2009.川滇地区地壳水平运动与变形场的演化特征及其机制讨论[J].地震研究,32(3):275-282.
杨国华,江在森,王敏.2006.印尼地震对我国川滇地区地壳水平活动的影响[J].大地测量与地球动力学,26(1):9-14.
杨国华,江在森,武艳强,等.2005.中国大陆整体无净旋转基准及其应用[J].大地测量与地球动力学,29(4):6-10.
杨国华,李延兴,韩月萍,等.2002.由GPS观测结果推导中国大陆现今水平应变场[J].地震学报,24(4):337-347.
杨国华,杨博,武艳强,等.2010.应变计算与分析的若干问题及有关偏差的修正[J].大地测量与地球动力学,30(4):59-63.
张军龙,陈长云,胡朝忠,等.2010.玉树MS7.1地震地表破裂带及其同震位移分布[J].地震,30(3):1-12.
张永生,马寅生,胡道功,等.2010.玉树地震地表破裂调查与灾后重建避让选址研究[J].地质学报,84(5):593-605.
张勇,许力生,陈运泰.2010.2010年4月14日青海玉树地震破裂过程快速反演[J].地震学报,32(3):361-365.
顾国华,张晶.2002.中国地壳运动观测网络基准站GPS观测的时间序列结果[J].大地测量与地球动力学,22(2):61-67.
国家重大科学工程“中国地壳运动观测网络”项目组.2008.GPS测定的2008年汶川MS8.0地震的同震位移场[J].中国科学,38(10):1195-1206.
江在森,马宗晋,张希.2003.GPS初步结果揭示的中国大陆水平应变场与构造变形[J].地球物理学报,46(3):352-358.
刘超,许力生,陈运泰.2010.2010年4月14日青海玉树地震快速矩张量解[J].地震学报,32(3):366-368.
王敏,沈正康,牛之俊,等.2003.现今中国大陆地壳运动与活动块体模型[J].中国科学(D辑),33(增):21-32.
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.
王琪,丁国瑜,乔学军,等.2000.天山现今地壳快速缩短与南北地块的相对运动[J].科学通报,45(14):1543-1547.
杨博,张风霜,占伟,等.2010.水平运动场滤波的尝试及其应变计算[J].大地测量与地球动力学,30(5):106-112.
杨博,张风霜,韩月萍.2011.球面水平应变场无偏差计算与滤波[J].地震研究,34(1):59-66.
杨国华,韩月萍,杨博,等.2009.川滇地区地壳水平运动与变形场的演化特征及其机制讨论[J].地震研究,32(3):275-282.
杨国华,江在森,王敏.2006.印尼地震对我国川滇地区地壳水平活动的影响[J].大地测量与地球动力学,26(1):9-14.
杨国华,江在森,武艳强,等.2005.中国大陆整体无净旋转基准及其应用[J].大地测量与地球动力学,29(4):6-10.
杨国华,李延兴,韩月萍,等.2002.由GPS观测结果推导中国大陆现今水平应变场[J].地震学报,24(4):337-347.
杨国华,杨博,武艳强,等.2010.应变计算与分析的若干问题及有关偏差的修正[J].大地测量与地球动力学,30(4):59-63.
张军龙,陈长云,胡朝忠,等.2010.玉树MS7.1地震地表破裂带及其同震位移分布[J].地震,30(3):1-12.
张永生,马寅生,胡道功,等.2010.玉树地震地表破裂调查与灾后重建避让选址研究[J].地质学报,84(5):593-605.
张勇,许力生,陈运泰.2010.2010年4月14日青海玉树地震破裂过程快速反演[J].地震学报,32(3):361-365.
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