Studies on the seismicity in Garhwal Himalaya, India

Abstract

The studies on the basis of the seismic records of seismic events in Uttaranchal a review of the events have been done and a probability 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 a 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 estimated to have future probabilities of earthquakes on 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 part of the Himalaya have the earthquake intensities varying from 4 to 6.0 on Richter scale in the geological past. The Kangra earthquake (1905) was recorded more than 7.0 Richter scale, Garhwal Earthquake (1883), (6.0), 'Uttarkashi earthquake' (1920), 1991 (5.6, 6.8) respectively, Chamoli earthquake (1999), 6.5 and the Dehradun earthquake of (1970). The approach followed for calculations of probabilities employ 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.