The modulation of groundwater exploitation on crustal stress in the North China Plain, and its implications on seismicity

摘要

In the North China Plain (henceforth, "NCP"), continuous over-exploitation of groundwater resources forms widespread groundwater depression cones. The removal of massive groundwater unloads the local lithosphere and therefore significantly perturbs regional crustal deformation and stress evolution patterns. Unfortunately, its ramifications to seismicity are yet poorly understood. In this work, we adopt a full three-dimensional (3D) viscoelastic finite element model to estimate the crustal deformation and stress changes triggered by groundwater unloading, and analyze its effect on major active faults by calculating the induced Coulomb stress changes. Meanwhile, variations on regional seismicity in association with the successive groundwater removal over the past 60 years in NCP is examined under scrutiny. The stunning results emphasize apparent crustal uplift occurs in most of the groundwater depression zones, reaching up 4.0 cm, and vertical normal stress increases by up to 70 kPa at the depth of 10 km, concentrating in the deepest groundwater depression cone. Overall, Coulomb stress significantly increases by above 10 kPa on major active faulting zones. Compared with the tectonic stress loading rate of 0.5 kPa/yr, the stress perturbation by groundwater removal is definitely non-negligible, which may eventually introduce an extra incentive to expedite the failure of active faults and even trigger earthquake events in NCP.