The influence of the South-to-North Water Diversion Project on the principal fault stresses of the North China Plain

SUMMARY Regarding the potential impact of groundwater storage changes on principal fault stresses and seismic activity in the North China Plain before and after the implementation of the South-to-North Water Diversion Project, this paper constructs a 3-D finite element model to calculate stress field variations induced by groundwater level changes from 1959 to 2023. Combined with Coulomb stress change calculations, the study evaluates the influence of groundwater extraction and replenishment processes on the crustal stress field before and after the diversion project. Research findings indicate that between 1959 and 2015, excessive groundwater extraction increased Coulomb stress on major faults across the North China Plain by up to 10 kPa. Following the official operation of the central route of the South-to-North Water Diversion Project in 2015, groundwater level changes induced fault Coulomb stress changes ranging between −2 and 2 kPa. Consequently, groundwater deficit prior to 2015 promoted regional seismic activity, while groundwater recovery after 2015 exhibited certain mixed effects on seismic activity, resulting from spatial distribution differences in groundwater deficit and replenishment across the North China Plain. This research provides scientific evidence for assessing the potential impact of the South-to-North Water Diversion Project on seismic activity and offers valuable reference for future earthquake risk assessment and groundwater resource management.