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基于2013年岷县漳县M6.6地震震源区及其邻区1999年以来的GPS观测资料,通过应变率动态特征分析、多期次GPS剖面分析和基线变形速率的分析讨论了地震的震前变形特征。GPS速度场和块体应变率表明,汶川地震的发生导致了柴达木地块运动与变形状态发生明显调整,但由于西秦岭北缘等深大断裂的存在,岷-秦地块对其响应不明显;GPS连续应变率显示,在汶川地震引起的区域地壳变形调整过程中岷县漳县地震震源区附近的应变积累速率有减缓的迹象;GPS剖面显示,平行于岷县漳县主破裂带的运动分量对汶川地震响应显著,汶川震后表现为剪切变形速率的增强,而垂直于主破裂带的运动分量则对汶川地震响应不明显;震中周边GPS基线变形速率表明,基线伸缩变化率总体呈现NW向拉张、NE向压缩状态,且拉张量明显小于压缩量。上述地壳变形动态特征表明西秦岭北缘断裂及其附近地区的应变积累水平和断层闭锁程度可能处于较高水平,在岷县漳县地震前该区表现出局部“硬化”迹象。
Based on the GPS observations since 1999 in Moxian County, Zhang County, Min County, Minjiang County and its neighboring areas since 1999, the dynamic characteristics of strain rate, multi-period GPS profile analysis and baseline deformation rate analysis are discussed. Deformation features. GPS velocity field and bulk strain rate indicate that the occurrence of Wenchuan earthquake resulted in obvious adjustment of the movement and deformation status of the Qaidam block. However, due to the existence of the deep and deep faults such as the northern margin of the West Qinling, the response of the Min-Qin block And the continuous GPS strain rate shows that there is a sign of slowing of the rate of strain accumulation near the source region of Zhangxian County in Minxian County during the adjustment of regional crustal deformation caused by the Wenchuan earthquake. GPS profiles show that parallel to the main fault zone of Zhangxian County in Min County The response of the Wenchuan earthquake to the Wenchuan earthquake was not significant. The baseline deformation rate of the GPS around the epicenter shows that the change rate of the baseline stretching rate The overall NW stretch, NE compression state, and tension is significantly less than the amount of compression. The above-mentioned dynamic characteristics of crustal deformation indicate that the strain accumulation level and the degree of fault blockage in the northern margin of the West Qinling are likely to be at a high level, showing some signs of “sclerosis” before the Zhangxian County earthquake in Min County.