Groundwater depletion in NW India and its response on crustal deformation

The GRACE measurements of the time-variable gravity field and mass change have helped in identifying regions of water reservoir over land, ice, and ocean, as well as in locating areas affected by drought and groundwater over-extraction. Studies indicate depletion in groundwater resources in North West (NW) India due to over-extraction from agricultural activities. The GPS measurements in the region indicate uplift rate varying from 1.5 to 4.2 mm/year caused by groundwater depletion-induced mass change. We observed a significant correspondence between the rainfall pattern, mass change derived from GRACE measurements, GPS measurements derived deformation, and well-level changes. Despite some marginal increase in rainfall in the past 3-4 years, the region is still experiencing over-extraction of groundwater due to increased demand for agriculture water. Although the Delhi Aravalli fold belt's paleo-structure primarily governs earthquakes in and around the Delhi region, we found no correlation between crustal strain rates and seismicity. Specifically, areas with high strain exhibited fewer earthquakes and less seismic energy release. GRACE data shows that prolonged groundwater over-extraction has resulted in significant negative anomalies in Equivalent Water Height (EWH). Although the magnitude of GRACE derived strain is very low, we find a good correlation between the GRACE-derived strain rates and seismicity. Our analysis demonstrates that groundwater over-extraction leads to substantial deformation in this region, which leads to earthquakes, and the observed uplift implies unclamping of faults, which may promote seismic events.