汶川地震产生的应变场和位移场

Displacement and strain field caused by Wenchuan earthquake

2008年5月12日汶川地震明显改变了区域地震的应变场。理解这种应变场的改变对周围断层构造加载进程和区域地震危险性的改变非常重要。本研究以汶川地震的破裂为驱动源,计算了该地震在近处造成的位移场和应变场。结果表明:该地震使得水平位移场断层南端的近乎东向运动逐渐转变为断层北端的东北向运动。震源附近有米级的位移量级。垂直分量与该地震的震源机制一致,西北盘上升、东南盘下降。断层附近的最大剪应变达3.2e-5,并随距断层的距离很快衰减。平均应变显示断层南部和中部主要表现为压缩,北部表现为拉张。

The 12 May 2008 Wenchuan earthquake has changed the regional strain field significantly. It is important to know how such a change affects the tectonic loading processes of the faults and therefore the seismic potential of the region. Utilizing the slip distribution of the Wenchuan earthquake as the driving source we compute the displacement and strain field near the source. Our result shows that the horizontal displacement field progressively rotated from east direction in southern end to northeast direction in the northern end. The magnitude near the source is in the order of meters. The vertical component is consistent with the Wenchuan focal mechanism with uplift in the northwest side and depression in the southeast side. The strain field is presented as mean strain and different strain. The different strain near the source is up to 3.2e-5 and decay rapidly as the distance from the fault. The mean strain shows predominant compression in the south and central part of the fault and extension in the north part.