长江三峡GPS处理结果和应变背景场

Results of the Crustal Deformation by GPS Survey and Horizontal Strain Rate Fields in the Three Gorges Area

采用BerneseGPSSoftware 4 .2对长江三峡工程诱发地震监测系统GPS监测网络 1998～ 2 0 0 3年的 6期观测数据进行了处理 ,结果表明 ,三峡库区与华南块体的水平相对运动在 0～ 3mm/a(± 0 .1～± 2 .0mm/a) ;蓄水导致的垂直形变区域主要集中在茅坪 香溪 巴东库段 ,近岸点垂直沉降的量级在 10～ 35mm左右 ,最大峰值区域香溪约 35mm(± 8.6mm) ,垂直形变沿远离库中心方向迅速衰减。采用贝塞尔双三次样条函数模型拟合该地区的应变率 ,推算各类水平应变场 ,结果表明 ,蓄水前各种应变背景在 10 -9/a～ 10 -10 /a量级。作为构造稳定地区 ,三峡库区近期因蓄水导致大规模形变 。

Bernese GPS Software 4.2 is used to analyze GPS data from six repeated surveys occupied by the GPS network of the Three Gorges Reservoir Induced Earthquake Monitoring System from 1998 to 2003.The result shows that the crustal deformation in the Three Gorges Reservoir area is less active with a marginally measurable rate of 0 and 3 mm/a(±0.1～ ±2.0mm/a) with respect to stable South China. Whereas, The vertical subsidence is about 10mm to 35mm alongshore after impoundment. We have simulated present-day GPS velocity solution with a bi-cubic spline interpolation function to estimate the horizontal strain rate fields before impoundment. The result shows that the tectonic deformation background of the Three Gorges area is slight (the horizontal strain rate is about 10 -9 /a to 10 -10/a).