Seismic risk assessment for central Indo-Gangetic Plains, India

Seismic hazard for the central indo-gangetic plains (CIGP) is either available in terms of generalized hazard spectrum as per IS 1893:2016 or in terms of only Peak Ground Acceleration (PGA) at the city level. Also, the study region falls in the seismic gap region, which has a potential for an earthquake of Mw>8.0. Hence, in this study, the seismic risk is assessed for the first time at the district level in the seismically critical region of India, the CIGP. In addition, the relative contribution of parametric and model uncertainties is also quantified from sensitivity analysis. Seismic risk results reveal that mud mortar bricks with temporary roofing (MMB) have the highest collapse probability of ~0.6. Further, brick walls with stone roof (BSR) and brick walls with metal sheet roof (BMS) also have high extensive and collapse damage compared to other building groups. These building types need immediate retrofitting / replacement for effective disaster mitigation. Also, geo-unit Allahabad, even though lying in zone II as per IS 1893:2016, has the most number of homeless and uninhabitable dwellings. Further, for a future earthquake of magnitude in the range of Mw 7.5 and 8.5, the expected financial loss might vary from 60 to 150 billion dollars, and the human loss might vary between 0.8 and 2.8 lakhs, respectively. Finally, results from this study will create awareness in the general public, policymakers, and structural engineers for taking up necessary mitigation measures on the existing buildings of CIGP for better preparedness from a future strong earthquake.