Hydrological response to earthquakes in the Haibara well, central Japan – I. Groundwater level changes revealed using state space decomposition of atmospheric pressure, rainfall and tidal responses

摘要: SUMMARY For the groundwater level observed at Haibara well, Shizuoka Prefecture, central Japan, time series analysis using state-space modelling is applied to extract hydrological anomalies related earthquakes. This method can decompose into five components: atmospheric pressure, tidal, and precipitation responses, observation noise, residual water level. The decomposed responses pressure are independently determined consistent with expected response surface loading. In 28 coseismic changes be discerned during period from 1981 April 1997 December. There a threshold in relationship between earthquake magnitude well–hypocentre distance, above which earthquakes cause All of well decreases, although 33 per cent estimated volumetric strain steps contraction, would increases. more closely proportional ground motion than steps, suggesting that due major drops contribution static rather small. Possible pre- or inter–earthquake have occurred may been caused by local aseismic crustal deformation.