利用GPS资料分析汶川地震前后川滇及其邻区水平运动及应变积累
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摘要
利用2004～2008年间,即2008年5月12日四川汶川8.0级特大地震前后川滇及其邻区(甘东南与陕西部分地区)GPS水平运动观测资料,借助形变应变场演化特征分析及负位错反演,研究了大震前构造变形特征与应变积累背景、同震变形及可能的影响区域。分析表明:(1)2004～2007年,龙门山中央断裂两侧出现的明显压性变化与阶段性应变积累特征对汶川大震有所反映(可能为中期即数年尺度6级以上地震的孕震背景),川滇菱形地块北—北东界、南界中—西段可能具有6级以上地震的孕震背景;而滇南—滇西南、甘川交界东段—甘川陕交界及其以北的甘南地块则反映6级左右地震的孕震背景信息。(2)2007～2008年,发震区呈现相当显著的逆冲兼右旋同震变化,大震对其附近的甘川交界—甘川陕交界、鲜水河断裂南段及"Y"字型断裂交汇区影响相对明显,对其应变积累状况的影响可能主要表现为一定程度的增强作用。
Based on the horizontal velocity data observed by GPS during 2004-2008,i.e.,before and after the Wenchuan MS8.0 earthquake,in Sihcuan-Yunnan and its vicinity(the southeastern Gansu and the part of Shaanxi),we study the preseismic tectonic deformation features and strain accumulation background,the coseismic deformation and its possible influence area combining with the analysis on the features of evolution of deformation-strain field and the inversion of negative dislocation.We conclude:(1)In the period of 2004-2007,obvious compression change and the phased feature of strain accumulation appeared in the two sides of the central Longmenshan fracture,which revealed the Wenchuan earthquake to a certain extent(it may be the medium-term background information of MS≥6.0 earthquake).The north-northeast boundary,the middle-west segment of south boundary of the Sichuan-Yunnan rhombus block probably had the background of MS≥6.0 earthquake preparation.The south-southwestern Yunnan,the area from the east segment of Gansu-Sichuan boundary to Gansu-Sichuan-Shaanxi boundary,and the southern Gansu block reflected the seismogenic information of the earthquake with magnitude about 6.0.(2)In the period of August 2007-June 2008,the Wenchuan earthquake area showed remarkable coseismic thrust and dextral deformation.The effect of the Wenchuan earthquake was comparatively obvious on the strain accumulation of Gansu-Sichuan boundary,Gansu-Sichuan-Shaanxi boundary,the south segment of Xianshuihe fracture and the Y-shape intersection region of fractures,which is possibly shown as a certain increase.
Based on the horizontal velocity data observed by GPS during 2004-2008,i.e.,before and after the Wenchuan MS8.0 earthquake,in Sihcuan-Yunnan and its vicinity(the southeastern Gansu and the part of Shaanxi),we study the preseismic tectonic deformation features and strain accumulation background,the coseismic deformation and its possible influence area combining with the analysis on the features of evolution of deformation-strain field and the inversion of negative dislocation.We conclude:(1)In the period of 2004-2007,obvious compression change and the phased feature of strain accumulation appeared in the two sides of the central Longmenshan fracture,which revealed the Wenchuan earthquake to a certain extent(it may be the medium-term background information of MS≥6.0 earthquake).The north-northeast boundary,the middle-west segment of south boundary of the Sichuan-Yunnan rhombus block probably had the background of MS≥6.0 earthquake preparation.The south-southwestern Yunnan,the area from the east segment of Gansu-Sichuan boundary to Gansu-Sichuan-Shaanxi boundary,and the southern Gansu block reflected the seismogenic information of the earthquake with magnitude about 6.0.(2)In the period of August 2007-June 2008,the Wenchuan earthquake area showed remarkable coseismic thrust and dextral deformation.The effect of the Wenchuan earthquake was comparatively obvious on the strain accumulation of Gansu-Sichuan boundary,Gansu-Sichuan-Shaanxi boundary,the south segment of Xianshuihe fracture and the Y-shape intersection region of fractures,which is possibly shown as a certain increase.
引文
顾国华.1990.形变监测网的基准与形变模型反演[J].地壳形变与地震,10(1):21-29.
江在森,张希,崔笃信,等.2001.青藏块体东北缘近期水平运动与变形[J].地球物理学报,44(5):636-644.
江在森,马宗晋,张希,等.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.
向宏发,虢顺民,徐锡伟,等.2000.川滇南部地区活动地块划分与现今运动特征初析[J].地震地质,22(3):253-264.
谢富仁,苏刚,崔效锋,等.2001.滇西南地区现代构造应力场分析[J].地震学报,23(1):17-23.
徐锡伟,程国良,于贵华,等.2003.川滇菱形块体顺时针转动的构造学与古地磁学证据[J].地震地质,25(1):62-70.
张希,江在森.1999.对华北GPS监测区近期地壳应变连续分布的估计[J].地震学刊,75(2):57-62.
张希,江在森,王琪,等.2003a.川滇地区地壳水平运动特征与强震关系研究[J].大地测量与地球动力学,23(3):35-41.
张希,江在森,王琪,等.2003b.1999～2001年青藏块体东北缘地壳水平运动的非震反位错模型及变形分析[J].地震学报,25(4):374-381.
张希,王双绪,崔笃信,等.2004.民乐—山丹地震的区域构造变形背景与中短期前兆[J].中国地震,20(3):238-246.
张希,江在森,王琪,等,2005a.青藏块体东北缘弹性块体边界负位错反演与强震地点预测[J].地震学报,27(6):620-629.
张希,江在森,王双绪,等.2005b.川滇地区地壳水平运动的弹性块体边界负位错模型与强震地点预测[J].地震研究,28(2):119-124.
M a tsu ura M,Jackson D D and Cheng A.1986.Dislocation model foraseismic crustal deformation at Hollister,California[J].JGR,91(B12):12661-12674.
O k ada Y.1985.Surface deformation due to shear and tensile faults in ahalf-space[J].BSSA,75(4):1135-1154.
江在森,张希,崔笃信,等.2001.青藏块体东北缘近期水平运动与变形[J].地球物理学报,44(5):636-644.
江在森,马宗晋,张希,等.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.
向宏发,虢顺民,徐锡伟,等.2000.川滇南部地区活动地块划分与现今运动特征初析[J].地震地质,22(3):253-264.
谢富仁,苏刚,崔效锋,等.2001.滇西南地区现代构造应力场分析[J].地震学报,23(1):17-23.
徐锡伟,程国良,于贵华,等.2003.川滇菱形块体顺时针转动的构造学与古地磁学证据[J].地震地质,25(1):62-70.
张希,江在森.1999.对华北GPS监测区近期地壳应变连续分布的估计[J].地震学刊,75(2):57-62.
张希,江在森,王琪,等.2003a.川滇地区地壳水平运动特征与强震关系研究[J].大地测量与地球动力学,23(3):35-41.
张希,江在森,王琪,等.2003b.1999～2001年青藏块体东北缘地壳水平运动的非震反位错模型及变形分析[J].地震学报,25(4):374-381.
张希,王双绪,崔笃信,等.2004.民乐—山丹地震的区域构造变形背景与中短期前兆[J].中国地震,20(3):238-246.
张希,江在森,王琪,等,2005a.青藏块体东北缘弹性块体边界负位错反演与强震地点预测[J].地震学报,27(6):620-629.
张希,江在森,王双绪,等.2005b.川滇地区地壳水平运动的弹性块体边界负位错模型与强震地点预测[J].地震研究,28(2):119-124.
M a tsu ura M,Jackson D D and Cheng A.1986.Dislocation model foraseismic crustal deformation at Hollister,California[J].JGR,91(B12):12661-12674.
O k ada Y.1985.Surface deformation due to shear and tensile faults in ahalf-space[J].BSSA,75(4):1135-1154.
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