Change in groundwater environment caused by the 2011 off the Pacific Coast of Tohoku Earthquake in the southern part of Sendai Plain

Abstract

Southern part of Sendai Plain was extensively attacked by tsunami caused by the 2011 off the Pacific Coast of Tohoku Earthquake. Continuous observation since 2008 has revealed that the groundwater level rose instantaneously right after the earthquake, and then the tsunami, which occurred about an hour later, involved the succeeding drastic rise. Salinity of groundwater was increased from below 0.7 mS/cm to at most 3 mS/cm, and has not been restored to the state before the earthquake.