SCENARIO EARTHQUAKE GENERATION FOR UTTARKASHI EARTHQUAKE 1991

Abstract

The occurrence of earthquakes, a global phenomenon, are one of the worst natural hazards in which several million lives have been lost and the loss of property runs into thousands of billions in spite of several technological, scientific and societal developments. These are the most devastating of all natural disasters because they strike enormous areas, resulting in massive death, injury, and damage of physical resources. They strike without notice and remain unpredictable, thus mitigation through proper measures is the most effective way to reduce their impact and losses. Uttarakhand experienced an earthquake of magnitude 6.8 on 20 October 1991. This study estimates the hazard in terms of ground motion fields PGA, spectral acceleration at 0.2 seconds and 1.0 seconds. And after estimating the seismic hazard of Uttarakhand, the risk in terms of social loss, number of casualties and injuries and economic loss has been estimated. Census of India 2011 has been used for the Demographic and housing data for various districts of Bihar. These data include population growth, population density, type of house existing in Uttarakhand, wall & roofing material, vulnerability of houses etc. This study also estimates the probable damages, economic loss, loss of lives, expected injuries that may occur in various districts of Uttarakhand, if 1991 earthquake intensity repeats in the recent years. Risk analysis of 1991 earthquake intensities has been estimated in the form of expected economic loss and social loss for various districts of Uttarakhand using an open-source software tool named Seis VARA (Seismic Vulnerability and Risk Assessment of Housing) in order to assess the seismic risk of housing stock. The PGA, SA (0.2) and SA (1.0) has been calculated using eight equations from 2008 and 2014. These GMFs are also calculated based on the site classification on the Shear wave velocity values. After calculating the PGA, the risk has been calculated in terms of social loss. In Uttarkashi the social loss in terms of casualty was 6348 persons in daytime and 5970 persons in night time. The economic loss was 526 Cr. in Uttarkashi. In Rudraprayag the social loss in terms of casualties was 3223 persons in daytime and 4289 persons in night time. The economic loss was 441 Cr. in Rudraprayag and 552 Cr. In Uttarkashi.