EARTHQUAKE LOSS ESTIMATION OF DEHRADUN CITY

Abstract

In view of spurt in unplanned urbanization of cities and population growth, the problem of probable maximum loss estimation due to major earthquakes has come into focus. The scientific approach to probable maximum loss estimation due to earthquakes for a site is based on simulating the occurrence of a specified earthquake hazard scenario superimposing the characteristics of exposure and vulnerability of different Model Building Types and integrating the interaction between the hazard and exposure to produce an estimated total loss. Earthquake loss for Dehradun city, a densely urbanized area situated in a highly seismic region at the foothills of Himalaya has been extensively estimated in the present study. The methodology relies on the estimation of seismic hazard for the study area which is calculated deterministically. Scismotectonic map provided by Seismotectonic Atlas of India (GSI, 2000) and past seismicity data by India Meteorological Department (IMD), New Delhi have been used for the estimation of maximum credible magnitude corresponding to each of the seismogenic sources. Peak horizontal ground acceleration has been estimated by using two different attenuation models. Proper site class of study area has been chosen as given by Ranjan (2005). Following these tasks exposure details of building inventory and population have been recorded based on recent census data and some previous studies on socioeconomic clustering of the city. Different Model Building Types (MBTs) have been identified in the city and capacity curve parameters are established for vulnerability analysis. Vulnerability class and damage state definitions have been taken from various research papers (Kappos et al., 2006). As a result, displacement demand and damage probabilities of various MBTs have been assessed using powerful software tool namely SeisVARA-Spectruxn (Haldar et al., 2013). Replacement costs according to socio-economic cluster of MBTs are set and loss models have been defined. Finally, the earthquake loss scenario of the city has been figured out in terms of casualty and direct economic loss in respect of maximum credible earthquake with the help of SeisVARA-Spectrum. This study gives an insight to earthquake loss estimation and the methodology can be applied to other Indian cities.