基于SRTM-DEM数据的三峡库区蓄水负荷模型及其地表重力与形变响应模拟

摘要

This paper aims to study relationships between water loading and its surface responses of gravity and crustal deformation over the Three Gorges Reservoir (TGR)according to time-varying water level data.Based on congruent relationship between high resolution SRTM-DEM data and topography of spatial boundaries of main channel and tributaries,we built a new water storage loading model under different water level in the TGR.Besides,mathematical expressions between water areas,volumes and water level data were fitted by power law relationships.Using new constructed water storage loading model,the elastic load response equation and mascon fitting method,we modelled the ground spatial distribution of the gravity and displacement fields when water level impoundment on the second and the third stages of the TGR.Meanwhile,time-varying water storage capacity model was obtained by Stokes spherical harmonic analysis (degree and order up to 60),and our results are analyzed with monitoring results from the GRACE data.GRACE-derived Terrestrial Water Storage (TWS)after using output from the CLM4.5 hydrology model shows very good agreement with the TGR prediction,but the difference between GRACE-derived and mascon fitting results may contain the groundwater seepage effect under huge water load pressure.The modelling results of this study will provide important basis of comparative analysis and related corrections to observations,and therefore,will be helpful to reveal masked relationships between the activities of landslips and reservoir induced earthquakes with the variation of reservoir’s water loading.%以三峡库区蓄水负荷变化为切入点，研究了库区因蓄水导致的地表重力与形变响应.通过高分辨率SRTM-DEM数据与三峡库区主干道及各支流边界的地形对应关系，构建得到不同蓄水水位下的蓄水负荷模型，并且给出了不同水位与库区整体库容量体积及受淹面积之间的数学拟合关系.在此基础上，结合弹性负荷响应理论及macson拟合方法，计算得到整个库区在蓄水第2阶段与第3阶段地表重力场及形变场的空间分布，以及库区蓄水库容量变化的60阶次球谐系数结果，并与GRACE监测结果进行了对比分析. GRACE去除CLM4．5模型后的陆地水储量可认为与三峡库区蓄水变化直接相关，两者之间的差异可能包含了在巨大水体负荷压力下出现的地下水渗透效应.本文理论模拟结果以期为实际观测资料的对比分析和相关校正提供支撑.有助于挖掘库区滑坡活动及水库地震等与库水负荷变化之间的关系.