Seismicity change associated with the impounding of major artificial reservoirs in Japan

Abstract

The change in seismicity associated with the filling of artificial reservoirs was investigated for 42 high dams in Japan. Based on a careful statistical analysis, a significant change in seismicity was found for ten dam areas at the 90% confidence level; eight cases of an increase in earthquake occurrence, and two cases of a decrease. It was also found that dam area earthquakes show remarkable seasonality with peak activity in the season of high inflow into the reservoirs. These results strongly suggest an effect of reservoir filling on local seismicity. To consistently account for the different types of seismicity change, an increase or decrease in earthquakes in the post-impounding phase, we proposed a model of reservoir-induced seismicity where the composite effect of loading and permeation of water causes a variety of seismicity patterns. According to the model, an increase or decrease in earthquake occurrence are attributed to differences in the tectonic stress field and geological conditions in the vicinity of a reservoir.