SPATIAL AND TEMPORAL VARIATION OF b-VALUE IN THE GARHWAL HIMALAYAN REGION AND ITS IMPLICATION AS AN EARTHQUAKE PRECURSOR

Abstract

The Garhwal Himalaya Region is one of the seismically active region of the Himalaya. This is characterized by the occurrence of moderate to large sized earthquake activity in this belt. The local earthquake data collected from the deployment of a 12 station seismological network by the Department of Earthquake Engineering, IIT Roorkee funded by the THDC India Ltd, Rishikesh around Tehri dam, the data for the period from 2008-2018 has been taken here for analyzing the seismic attributes in the Garhwal Himalayan Region i.e. the variation in value of b as an Earthquake precursor in terms of Spatial & Temporal variation. The study region i.e. Garhwal Himalaya region has been divided into Four Cluster with these Latitudinal & Longitudinal position i.e. 77.5ºE-79.0ºE to 29.50ºN-30.7ºN (Tehri Region) , 76.70ºE-78.60ºE to 30.70ºN-32.0ºN (Himachal Region) , 79.70ºE-80.75ºE to 29.20ºN-30.70ºN (Pithauragarh Region) & One Diagonal Element i.e. (Chamoli-Uttarkashi Region) having coordinates 78E, 30.70N - 80E, 30.5N to 79.60E, 29.90N - 78.60E, 31.20N) for carrying out spatial variation in b-value & the same has been analyzed for temporal analysis of the data. The Mc, b and a-values has been estimated with respect of each zone, and the variations in the values of these parameters has been analyzed. The catalogue i.e. the chosen data for the period from 2008-2018 contains, the total no. of events 3972 in magnitude ranges 0 <M< 5.0 & Maximum no. of events has occurred in the range of 1 <M< 2.0, which has been shown clearly in figure no. 4 of Histogram of magnitude. The whole Garhwal Himalayan Region has divided into four cluster for area specific studies and among the four regions, the Tehri region is showing lesser b-value i.e. 0.71, it implies that this region is still stressed and there are high chances of near future Earthquake in this region