Investigation of effect of Yamchi dam reservoir impounding on areal seismicity rate

Yamchi dam was constructed in 2005 in south of Ardabil. In order to investigation of effect of reservoir impounding on seismicity rate changes of dam area (30 km radius) and proving of Reservoir Induced Seismicity, Firstly, structures were determined and surveyed and their Quaternary and Recent activities documented. Then, the earthquake catalogue was completed and historical and instrumental seismicity investigated. Finally, the completed magnitude and b-values were calculated and then, the impounding of reservoir effect on seismicity rate changes studied. The results shown that two main Ardabil and Sarein faults, with Quaternary and recent activities located in 30 km radius of dam site and many of earthquakes taken placed in cross cut of these faults. Investigation of effect of impounding of reservoir on seismicity rate, as cumulative diagram of released energy relative to reservoir volume changes, determined four stage of b-value and energy released changes. Impounding of dam reservoir, caused to rising of seismic activities as increasing b-value and diagram slope of releasing cumulative energy. This phenomenon proved that low magnitude/ high magnitude earthquake ration was increased as occurrences earthquakes with M<4 in depth <5 km.