Hydrological response to the Sea of Galilee 2018 seismic swarm

Abstract Co-seismic and post-seismic groundwater response to the Sea of Galilee 2018 seismic swarm, along with other teleseismic earthquakes are analyzed in nine water pressure monitoring wells, with high sampling rates (40 sps). The largest event of the swarm (Mw 4.6) caused significant water level oscillations of 0.216 bar (2.16 m) and sustained water level drop of 0.121 bar (1.21 m). The response of groundwater to this event and two other distant large events include co-seismic oscillations, co-seismic undrained sustained change, and post seismic drained change. In addition, the proximity of the earthquake swarm to high resolution monitoring wells provides an opportunity to analyze the changes in the oscillations’ amplitudes of most events. The ratio of the water level to ground motion acceleration amplitudes increased after the Mw 4.6 event, suggesting that the aquifer poro-elastic properties have changed. These co-seismic amplitude changes are more sensitive measure than the water level response to earth tides that showed no significant change in the phase and amplitude associated with any of the events. The maximum amplitude of the oscillations is correlated to the amount of drained response, suggested to be caused by activation of a nearby fault and drainage of water between aquifers. The undrained behavior is related to poro-elastic properties changes within the aquifer and depends on the duration of the oscillations. Details of the groundwater high sampling rate can shed light on deformation processes that were described previously as step like changes.