The studies on the history of the seismic events in the part of Garhwal, Himalaya has been carried out. On the basis of the seismic records of seismic events n Garhwal a review of the events has been done and probabilities of the earthquake has been workout in the part of Garhwal-Kumaun-Himalaya in Uttaranchal. In the southern part of outer Himalaya, thrust zones are expected to produce long-term probabilities of large earthquakes of magnitude more than 6, on Richter scale which have on and average 5 to 20 mm reactivation and neotectonic upliftments along the shear zones. These zones have been estimated to have future probabilities of earthquakes in these areas, which are based on the historical seismic records, the long-term slip rate and the displacement caused by the previous seismic events. The historical records of seismic events in these parts of the Himalaya have the earthquake intensities varying from 4 to 6.0 on Richter scale in the geological past. The Kangra earthquake (1905) recorded more than 7.0 on Richter scale, Garhwal Earthquake (1883) 6.0, Uttarkashi earthquake (1920 and 1991) 5.6 and 6.8 respectively, Chamoli earthquake (1999) 6.5, and the Dehradun earthquake (1970) 5.6. The approach followed for calculations of probabilities employs the estimated recurrence times with a model that assumes probability increases with elapsed time from the large earthquake on the fault/thrust zone areas. Through the calculated probabilities, the estimated natural disaster/ hazards in the newly born state of Uttaranchal in Himalayan belt can be reduced.

The past records of the seismic events along the Himalayan belt in Garhwal Himalaya Himachal-Nepal, with the geological, structural, seismic observation stations, provides the principle means for evaluating the potential for future earthquakes. After the Kangra- 1905 earthquake, this area has experienced many earthquakes of lower magnitude, which have caused in many areas formation or damaging of lakes, and flood (1978) in Bhagirathi and Alaknanda rivers in Uttaranchal Himalaya. The Uttarkashi earthquake (October 1991; 6.8 on Richter scale) and Chamoli earthquake (March 28, 1999; 6.5 on Richter scale) caused a havoc, including deaths, injuries, loss of properties, development of cracks on the ground and hill slopes, and many neotectonic activities such as reactivation of landslides, hill slopes, and mass movement. Both these earthquakes were located in the 200-km wide main central thrust zone areas.

The main reasons for undertaking the calculation of 20 years probabilities due to the recent earthquakes and second consideration of several feature of regional seismicity that may indicate an increased potential of large earthquake; also because of these earthquakes the slip rate and neotectonic activities are higher. The Uttaranchal area has a wide zone of thrust trending NW-SE in Higher/Central Himalayan area as well as in lower Himalayan, which is characterized by the presence of MBT in the SW part and Krol/Garhwal thrust, Almora thrusts in the lesser Himalaya and MCT distributed in the north (Figure 1). For the harvesting and harnessing of water resources, the government has planned 62 major/minor dams on the various river valleys to generate hydroelectricity and for irrigation. Since the rocks of terrain are highly sheared and fractured with a number of thrust zones, and fault zones, it may not be able to bear the weight of the water column and the load of the structure; it will also trigger induced earthquakes in the near future.

Earth Sciences Journal, Palaeoenvironmental Studies, Rajapuram and Somanapally Sandstones, Palaeocurrent Analysis, Crossbedding, Proterozoic Rocks, Godavari Valley, Pakhal Sandstones, Polycrystalline Grains, Precambrian Sediments, Bimodal System.