Local groundwater and tidal changes induced by large earthquakes in the Taiyuan Basin, North China from well monitoring

Abstract Seismically induced water level and tidal behavior changes were analyzed in four wells (TY, QX, XY and JX) in the Taiyuan rift Basin. One of the wells (JX) with higher storativity and higher permeability mainly recorded oscillation changes, which suggests that higher seismic energy density might be required to cause sustained water level changes in such wells. The other three wells recorded sustained water level changes following multiple large earthquakes, in which two of the wells located within fault damage zone or developed fracture area showed synchronized water level and tidal behavior changes after earthquakes. Moreover, the two wells recorded different tidal behaviors (positive or negative correlation between tidal factor and phase shift), which suggested that far field earthquake caused the mixture of vertical flow and radial flow. We suggest that local hydro-geological setting and fissures connected to the aquifer play an important controlling role in earthquake-induced water level and tidal behavior changes.