Induced Seismicity in Sidi Salem Dam, NW Tunisia

Abstract

The Sidi Salem reservoir was built in Beja, a semi-arid region in Northwestern Tunisia, for such purposes as the protection of the lower valley against floods, irrigation, water supply, and power generation. It is the biggest reservoir in Tunisia. It is a 73-m high, 814 Mm³ water storage capacity compacted-earth dam. The seismic events in the studied area were monitored by a seismic network operated by the National Institute of Meteorology. The main aim of this study was to establish the correlation between water level in the reservoir and the induced seismicity. The first earthquake susceptible to be an induced event was found out in 1987 with magnitude of 5 after complete filling of the dam. Shortly afterwards, there was an increase in the number of seismic events, and many earthquakes were noted. It was suggested that this induced seismicity took place after the reservoir loading effect and also the postponed effect of the diffusion of pore pressure. The comparison between the seismic data and reservoir water level indicated that there was a correlation between the changes in the water level and the seismic activity.