The Tehri dam project is located in the Uttarakhand state of India and is the largest hydro development project of south-east Asia. The major project features include: a 260.5 meter high earth and rock-fill dam with a storage volume of 3.54 km3, located near Tehri on the Bhagirathi River; an underground power house of one thousand megawatt, a proposed power house of one thousand megawatt capacity on the left bank; and a balancing reservoir at Kotashwar dam with four hundred megawatt capacity. The region around Tehri is dominated by convergent tectonics attributed to continent-continent collision. The high level interplate seismicity of the region is characterized by occurrence of moderate to large-sized earthquakes and is ascribed to the Alpide seismicity belt that passes through the Himalaya. The seismicity of Tehri region has attracted considerable attention in the recent past from public as well as from scientific community because of building a high dam at Tehri and due to the occurrence of two moderate earthquakes, namely the Uttarkashi earthquake of 1991 (mb3 =6.6) and Chamoli earthquake of 1999 (mb3 =6.4). Seismicity and seismotectonics of the Garhwal Lesser Himalaya in general and of Tehri region in particular have been studied using data of teleseismic earthquakes and local earthquakes. This paper describes the characteristics of seismicity based on local earthquake data and provides brief account of studies related to earthquake source parameters and attenuation properties of the region around Tehri computed using limited digital data.
