汶川8.0级地震时徐州台地震动和形变同震响应分析

Earthquake Motion and Co-seismic Deformation Response of Wenchuan M8.0 Earthquake at Xuzhou Seismic Station

通过对汶川8.0级地震和6次强余震时徐州地震台的形变同震响应和地震位移量研究,计算了汶川地震主震发生时地震面波到达徐州的时间和位移量,统计了汶川8.0级地震及其强余震引起的同震阶变时间参数、幅度参数和阶跃形态。研究结果表明:①该台4套形变观测均有较高的同震响应能力,同震阶变的开始时间与主震面波到达徐州台的时间基本吻合,可以认为同震应变阶和同震波是由强震面波引起的,是一种叠加在体应变固体潮曲线上的高频变化,并呈现快速振荡衰减的形式。②同台同岩性的不同形变观测对同一个地震的响应是不同的,阶跃形状、响应大小、响应时间、变化幅度都有较大的差别,这种差别更多的是反映了仪器本身的性能、观测精度、频率响应的不同,并不是应力场变化和构造特征的差异。③汶川地震引起的徐州地区应力变化以压应力为主,大地震的动态应力触发作用对远场的应变变化具有重要影响。

Co-seismic changes of Wenchuan M8.0 earthquake and six strong aftershocks were recorded by 4 digital deformation instruments at Xuzhou seismic station at an epicentral distance of 1392 kin. The result shows that the strain-step changes and wave motions are caused by the arri val of the corresponding surface waves. The shape and size of the step changes and the response time recorded by different instruments were different, even they were located in the same rock body only 7.65 m to 10.57 m apart. This difference is probably a refleetion of different instru- ment properties, such as sensitivity and frequency response. The earthquake-causing stress chan- ges, which were mainly compression in Xuzhou, had an important triggering effect on far-field strain changes.