汶川地震震前与同震断层滑移的比较分析

Comparsion of Pre-earthquake and Coseismic Fault Slip of the 2008 Wenchuan Earthquake

本文利用GPS观测的1999—2007年汶川震前3期地表变形数据和2008年汶川同震地表变形数据,结合地震位错理论,通过高斯变换和坐标旋转建立断层模型,运用遗传算法,反演了龙门山断裂带断层震前3期和同震滑动参数。结果表明龙门山断层震前3期平均走滑位移为-5.39mm,倾向位移为2.66mm,与同震断层滑移相比较,发现震前断层的滑移趋势与同震断层滑移一致,均为逆冲兼右旋的挤压运动。比较震前3期逆冲方向的滑移量,发现逆冲滑移有加速的现象。并根据震前和同震的断层滑动量估算了汶川地震复发周期。

In order to get the acknowledge about the pre-earthquake fault slip and its relationship with coseismic slip of the 2008 Wenchuan Earthquake, this paper inverts the GPS measurements from 1999 to 2007 and the coseismic measurementsto infer the pre-earthquake and coseismic slip characteristics of Longmenshan fault. The earthquake dislocation theory and the genetic algorithm are used in the inversion. It is shown that the mean strike-slip from 1999 to 2007 is about 5.39 ram, and the dip slip is almost 2.66 ram. This pre-earthquake slip tendency is consistent with the coseismic reverse and right-lateral slip. The results of the dip slips occurred in 1999 to 2001, 2001 to 2004 and 2004 to 2007 before the 2008 Wenchuan Earthquake indicatethat the dip slip is accelerating with time. This acceleration slip may be a precursor of earthquake. Finally, based on the inversion results of the pre-earthquanke and coseismic fault slip, we estimate the recurrence period of Wenchuan earthquake.