Earthquake induced Deterministic Damage and Economic Loss Estimation for Kolkata, India

The city of Kolkata, the State Capital of West Bengal is jolted by earthquakes time and again from the tectonic regimes of the Central Himalaya, highly seismogenic Northeast India and the active tectonics of Bengal Basin which is a pericratonic tertiary basin on which the City is located. Earthquake disaster mitigation and management necessitates seismic hazard assessment for the generation of design response spectra at a site of interest with a zone factor for the computation of seismic coefficient to be adapted in building codes. The surface consistent probabilistic seismic hazard model of Kolkata for 475 years of return period have been used for modeling of damage potential of buildings, human casualty and economic loss employing the widely used SEismic Loss EstimatioN using a logic tree Approach (SELENA) in a relational analysis protocol considering eleven model building types. The demand spectrum curve of a spectral acceleration through a judicious interaction with the building capacity curve and fragility curve yields the damage state probability of the same in terms of slight, moderate, extensive and complete. Human casualty levels are also computed using SELENA for three different times of the day viz. Night, Day and Commuting time. The economic loss to the tune of ~231 billion of Indian Rupees due to building damage only have been estimated within 300 socioeconomic clusters in the City. It is expected that this model will go a long way in safe urbanization process with well-defined disaster mitigation and management guidelines for the city of Kolkata.