SEISMIC HAZARD ASSESSMENT OF KANGRA REGION

Abstract

The study is made to determine the probabilities for the return periods of earthquakes in the area in and around Himachal Pradesh bounded by 300 - 330 N latitude and 750 - 790 E longitude. Annual Extreme Values Method of Gumbel (1958) is used by selecting the earthquakes equal or greater than M = 4 that occurred for the time interval 1963-201 2. Also, the methodology used to estimate the magnitudes of future earthquakes is by statistical method developed by Richter and Gutenberg (1942) in which all the earthquakes of the past of any size may be taken into calculations. According to this method proposed by Gumbel, the distribution of the annual maximum earthquake magnitudes is given which yielded that the probability of an earthquake occurrence of magnitude = 7 in 100 years is 75 percent and its return period is 70 years. The seismic hazard of Dharamshala in terms of Peak ground acceleration was determined using the attenuation relationship of Abrahamson and Lithehiser (1989) and Sharma (1998).The values of PGA using the above relations were found to be 0.58 and 0.33 respectively.Further the region is divided into 0.5° latitude by 0.50 longitude grids and the peak ground acceleration at the center of each grid is calculated. The PGA was found to vary between 0.11g to 0.36g. The contour map for the region was also prepared. An arbitrary RCC 4 storey building was designed at Dharamshala and was analysed for the response spectra generated from the PGA calculated at the region. The base shear acting on this RCC building was found to be 1105.85 kN.