Groundwater is a vital water resource in the world. The storage in an aquifer is a capability of water volume that can release from or take into the aquifer. This study represents an efficient process to determine the groundwater storage in the deep aquifer near the Western Pacific Ocean using the Tohoku earthquake activity (2011), Japan. Groundwater levels in monitoring wells responded to seismic activity have been demonstrated. Estimating the time-dependent groundwater head and seismological displacement spectra, the period varied between 21.3 s to 32 s of Rayleigh waves propagating from the epicenter to the receiving stations. It addresses the storage coefficient of a deep and confined aquifer in the order of 10-5 to 10-3 regarding the storage property of subsurface hydrology in the studied sites. Practically, estimating groundwater storage in the deep aquifer by earthquake activity becomes achievable.