三峡库水位变化过程中的地壳垂直形变与重力变化监测

监测三峡库水位变化过程中的地壳垂直形变和重力变化,对三峡水库的安全运行和区域地质灾害监测防治等具有重要意义。本文从直接计算、实际测量和综合解算3个方面研究了三峡库水位变化过程中地壳垂直形变和重力变化。基于资源三号卫星影像提取的水体数据,结合水位数据,直接计算了三峡水库蓄放水从145~175m每隔5m的影响,地壳垂直形变最大可达30mm,对重力影响超过20μGal(1Gal=10~(-2) m/s~2)的范围距离长江中心线约2km内。库区较近的巴东CORS站(ES13)能够实际测量到库水位变化过程中的地壳垂直形变。由于目前三峡库区的CORS站和重力台站数量较少,分布不均,还不能满足紧密跟踪三峡库水位变化过程中的监测需求。利用三峡地区26座CORS站和部分重力台站数据,基于负荷形变理论和球谐分析方法,综合解算了库水位变化过程中的地壳垂直形变和重力变化,与实际CORS监测结果一致。通过对比分析发现,基于CORS站网的综合解算,能够有效提升对库水位变化过程中的地壳垂直形变和重力变化的监测能力。

Monitoring Vertical Crustal Deformation and Gravity Variations during Water Level Changes at the Three Gorges Reservoir

Monitoring vertical crustal deformation and gravity changes during water level changes at the Three Gorges reservoir is important for the safe operation of the Three Gorges Dam and for the monitoring and prevention of a regional geological disaster.In this study, we determined vertical crustal deformation and gravity changes during water level variations of the Three Gorges reservoir from direct calculations and actual measurements and a comprehensive solution.We used water areas extracted image data from the ZY-3 satellite and water level data to calculate gravity changes and vertical crustal deformation caused by every 5m change in the water level due to storage and drainage of the Three Gorges reservoir from 145m to 175m.The vertical crustal deformation was up to 30mm.The location of gravity change above 20μGal(1Gal=10-2m/s2) was less than 2km from the centerline of the Yangtze River.The CORS ES13 in Badong, near the reservoir, measured the vertical crustal deformation during water level changes.Because of the small number of CORS and gravity stations in the Three Gorges reservoir area, monitoring deformation and gravity related to changes in the Three Gorges reservoir water level cannot be closely followed.Using 26 CORS and some of the gravity stations in the Three Gorges area and based on loading deformation and the spherical harmonic analysis method, an integrated solution of vertical deformation and gravity variations during water level changes of the reservoir was determined, which is consistent with the actual CORS monitoring results.By comparison, we found that an integrated solution based on a CORS network can effectively enhance the capability of monitoring vertical crustal deformation and gravity changes during water level variations of the reservoir.