[S-CG59] Crustal fluids and deformation

[SCG59-P05] Changes in groundwater level associated with earthquakes at the Takarazuka Observatory in the last two decades

*Norio Matsumoto¹, Tsutomu Kiguchi¹ (1.Tectono-Hydrology Research Group, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST))

Keywords:Changes in groundwater level associated with earthquakes, Takarazuka Observatory

We observed eight postseismic increases in groundwater pressure were observed at Takarazuka observatory (TKZ) in the last two decades. Shapes of the curves in the three largest increases are relatively similar: it might be same mechanism for the postseismic increases. Recovery test shows that the postseismic increases may not be caused by sudden increase of pore pressure near the TKZ well. We compare postseismic changes at TKZ with the postseismic changes in groundwater level at four observatories which are inconsistent with poroelastic theory. The threshold of earthquakes with postseismic changes in groundwater level at TKZ locates more upper-left side than the previous results of other observatories in the Magnitude - Distance plot.