Groundwater level and temperature changes following the great Tangshan earthquake of 1976 near the epicenter

Several meters of rise in groundwater level with significant changes in groundwater temperature were observed near the epicenter of the 1976 Tangshan earthquake-an intraplate earthquake with a magnitude of M (S)=7.8 that occurred in northern China. The origin of the groundwater level rise, however, remains a mystery. Studying the groundwater level rise can provide insight into the faulting process and has implications for water resources. In this study, we analyze the indications of the groundwater temperature data on the characteristics of the rising groundwater. The results show that the upward flow was maintained for approximately 5 days, and the depth of the rising groundwater was about 1-2 km. We then examine the groundwater level and temperature data with several reported models in order to explain the cause of the groundwater level rise. The results indicate that the groundwater level rise is attributable to the earthquake-induced enhancement of vertical hydraulic connection between the shallow and deep aquifers, leading to the upwelling of deep fluids that causes the groundwater levels to rise.