Abstract
Assessment of the geological environment for the long term safety of geological disposal systems for high-level radioactive waste requires consideration for any phenomenon resulting in cumulative change to the geological environment at the regional scale. Groundwater pressure changes induced by earthquakes, for example, are one of the phenomena to be considered. Groundwater pressure changes induced by earthquakes have been observed during long-term monitoring carried out by Japan Atomic Energy Agency in the Tono Area, Gifu. In this paper, the observations of groundwater pressure change induced by earthquakes are summarized. In addition, an impact on groundwater flow conditions induced by earthquakes is discussed. As a result, it is inferred that influence of groundwater flow condition induced by the three earthquakes, Tokachi-oki Earthquake in 2003, the off the Kii Peninsula Earthquake in 2004 and the Suruga Bay Earthquake in 2009, are temporary. On the other hand, the groundwater pressure changes after the 2011 off the Pacific coast of Tohoku Earthquake seem different from those by the three earthquakes and it is necessary to continue the observation of the groundwater pressure. In addition, this paper shows that it is important to focus not only the change of groundwater pressure but also the change of the hydraulic gradient and hydraulic permeability in evaluating the long-term stability of groundwater flow condition.
