抄録
Groundwater observation wells have been bored in 42 sites in Tokyo Metropolis. Large fluctuations of groundwater levels were observed after the 2011 off the Pacific coast of Tohoku earthquake at 102 observation wells in Tokyo. In this study, the fluctuation patterns of monthly groundwater levels caused by the earthquake were investigated using Self-Organizing Map (SOM). The SOM application classified the groundwater level fluctuation pattern into four clusters showing exclusively distinguishable patterns. sequently, the results show that the monthly fluctuation pattern of more than half observation wells changed after the earthquake. Additionally, an increase can be seen in the confined groundwater level in Musashino Plateau following a lower amount of groundwater being pumped due to the earthquake. Furthermore, all unconfined observation wells, and most of the observation wells at depths above 70m and those south of Tama River showed no significant changes following the earthquake.
