Preliminary Study of Reservoir Triggered Seismicity in the Vicinity of Tarbela Dam

Tarbela dam is situated on the lesser Himalayas of northern Pakistan which is a very active tectonic region. On regional scale the Main Boundary Thrust, Punjal Thrust Structure, Indus Kohistan Seismic Zone and Hazara Kashmir Syntaxis are major active fault systems which increase the vulnerability of this region to catastrophic earthquakes. Hazara, Salkhala, Kingriali and Tanawul formations exist in the region around the dam. Seismic data from 1973 to 2012 from a specialized network of seismic stations are incorporated in this study in order to carry out an investigation based upon the reservoir triggered seismicity (RTS). The hydrological data of Tarbela dam reservoir is also used to find out whether a relationship exists between the rate of earthquake occurrence around the lake of Tarbela dam and the fluctuation in water level during various seasons throughout the year. An extensive work in this article deals with the various aspects of the b-value. Three concentric circular regions, encompassing the reservoir of Tarbela dam, are defined to identify geological boundaries of the study region and filtering of the seismic data. Although the number of earthquakes vary significantly from larger to smaller zone the b-values does not deviate much from an average value of 0.64 for the whole period between 197