【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。更多还原

【Abstract】 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.更多还原