利用时序InSAR技术反演邯郸平原区地表形变与含水层参数

邯郸平原区承压地下水长期处于严重超采状态, 导致大面积地面沉降, 直接威胁到该地区重大基础设施安全.因此, 查明地面沉降时空演变特征, 厘清承压地下水变化与地面沉降的耦合关系, 对预防和治理地面沉降地质灾害具有重要意义.本文利用Sentinel-1A数据进行时间序列分析, 获取了2015—2019年邯郸平原区地表形变时空分布结果, 并结合水头数据分析了含水系统对水头变化的不同响应.利用谐波函数分离了地表形变及水头变化的季节性变化, 并用其估算了邯郸平原区空间差异变化的弹性骨架释水系数; 基于顾及弱透水层延迟排水的一维水头变化-形变模型, 反演了非弹性骨架释水系数和时间常数.结果表明: (1)邯郸平原区以沉降为主, 最大沉降速率可达14 cm·a^-1; 通过与水头数据对比发现该地区地面沉降主要是由承压含水层水头下降及弱透水层的延迟排水引起.(2)水头的季节性变化引起了明显的季节性形变, 沉降区季节性形变幅度可达25 mm, 峰值时间为1—3月.(3)邯郸平原区弹性骨架释水系数介于1.51×10^-3~4.05×10^-3之间, 与抽水试验结果较为相符; 非弹性骨架释水系数为3.62×10^-2~4.57×10^-2, 时间常数为0.47~0.77 a.本研究表明时序InSAR技术在含水层参数估算, 地下水超采相关的地质灾害监测方面有良好的应用潜力.

Estimation of the land deformation and aquifer parameters in the Handan plain using multi-temporal InSAR technology

The long-term overexploitation of confined groundwater in the Handan plain leads to regional subsidence, threatening major infrastructure security. Thus, it is vitally important to investigate the spatiotemporal characteristics of land subsidence and clarify the coupling of deep groundwater change and land subsidence for land subsidence disasters prevention and control. In this study, we apply the multi-temporal InSAR method to detect the spatiotemporal variations of land deformation in the Handan plain with Sentinel-1A data from 2015 to 2019, and analyze the aquifer system response to hydraulic head changes. Seasonal signals in land deformation and head data are isolated by harmonic function to derive the spatially heterogeneous elastic skeletal storativity. Moreover, according to the one-dimensional head change-delayed land deformation model, we estimate the inelastic skeletal storativity and time constant. The results indicate that: (1) The Handan plain is dominated by land subsidence with the maximum rate of 14 cm·a-1. Comparison between the subsidence and head change suggests that the subsidence is mainly caused by the head drop in aquifers and delayed drainage of water from aquitards. (2) The seasonal fluctuation in head leads to the obviously seasonal deformation, the amplitude of seasonal deformation can reach up to 25 mm, and the peak time ranges from January to March. (3) The values of elastic skeletal storativity range from 1.51×10-3~4.05×10-3 that agree well with those derived from pumping tests, the inelastic skeletal storativity is 3.62×10-2~4.57×10-2 and the time constant is 0.47~0.77 years. This study demonstrates the potential of using multi-temporal InSAR technology to characterize aquifer parameters and monitor the geological disasters caused by groundwater overexploitation.