History of Seismic Events in Garhwal Himalaya, India
The IUP Journal of Earth Sciences, Vol. 6, No. 1, January 2012, pp. 36-57
Posted: 13 Sep 2012
Date Written: September 12, 2012
Abstract
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 in 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.
Keywords: Himalayan thrust, Recurrence time, Elapsed time, Rupturing
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