鲜水河断裂带北段GPS测量及其运动特征

CURRENT CRUSTAL DEFORMATION IN NORTH SECTION OF XIANSHUIHE FAULT CONSTRAINED BY GLOBAL POSITIONING SYSTEM

鲜水河GPS监测网由18个沿鲜水河断裂带分布的点组成.1991年对该网进行了首次观测,1996和2000年进行了两期整网复测.本文利用该网1991和2000年的二期GPS观测资料结合川西地区20世纪70年代以来的常规大地测量资料,计算给出了这一强震活动带现今运动图像:由测区的北西虾拉沱测点到南东的乾宁测点水平位移速率逐渐增大,而断层两盘的相对运动不明显.表明利用短边GPS测量可有效监视活动断裂带两侧一定区域的地壳运动.对比有形变测量资料以来川西地区6级以上地震分布的特点,认为可根据鲜水河断裂带断层两盘的相对运动和跨越断层的地壳整体运动的强弱这两种运动图像来研究区域强震的活动特征.

Global Positioning System(GPS) network on north section of Xianshuihe fault is arrayed in 1991 and measured 3 times in 1991,1996 and 2000.The result shows that: (1) The displacement velocity increase regularly from Xialatuo station in rate of 8.5 ±0.8 mm/yr with SE direction to Qianning station in rate of 13.8±1.7 mm/yr with EW direction along the fault.(2) On the Daofu measure profile which cross the fault,the velocity rise as stations are far from the fault on the SW wall of fault.(3) The relative movement of the stations on two walls of the fault is little so we infer that at present the slip rate of the Xianshuihe fault is not obvious that is in accordance with the conventional geodetic data along the fault. As the conclusion,in the period of minor activity of Xianshuihe fault,the Chuandian and Chuanqing plates should be thought as a whole when studing its seismic hazard,in other time we should put our studying focal on the activity of the fault and the relationship with the seismic hazard.