Preliminary evaluation of induced seismicity at the Karkheh dam site in southwest Iran

The reservoir-induced seismicity (RIS) at the Karkheh dam site with a reservoir capacity of about 7.4x109 meters is investigated. Based on the assessment of the seismicity of the dam site in equal time periods before and after reservoir impoundment, it was found that the number of earthquakes have been tripled after impoundment, while their magnitudes and focal depths become smaller. The average earthquake depth before the impoundment was about 40 km whereas it decreased to about 23 km after that. Based on this study, it is concluded that RIS is happening in the Karkheh dam site and it is necessary to study the possible associated hazards.