Probabilistic seismic hazard analysis of the Coimbatore region, Tamil Nadu using a logic-tree approach

The Coimbatore corporation area is comprised of very densely occupied residential and commercial buildings which are prone to future earthquakes. Probabilistic Seismic Hazard Analysis (PSHA) was carried out for the study region using the Classical Cornell approach and the logic-tree approach. A combination of 45 linear/fault sources and an areal source with a 500 km radius has been considered for the study. An updated earthquake catalogue has been compiled from various works of literature and authorized organizations. The collected earthquake catalogue of various magnitude scales has been homogenized into a uniform moment magnitude scale \(\left({M}_{w}\right)\). Fore-shocks and after-shocks have been removed from independent events using one of the declustering algorithms. The seismicity parameters have been evaluated using the Guttenberg–Richter recurrence law. A hybrid GMPE composed of three attenuation relationships was used to obtain the ground motion parameters for the study region. The contour maps of Peak Ground Acceleration (PGA) and Peak Spectral Acceleration (PSA) for the bed-rock condition have been presented in terms of 10 and 2% Probability of Exceedance (PoE) for the return period of 475 and 2475 yr, respectively. The Uniform Hazard Response Spectra (UHRS) for Coimbatore city has been compared with (IS 1893-I-(2016) Criteria for earthquake resistant design of structures. Part 1: General provisions and buildings; Bureau of Indian Standards). As a result of deaggregation, the predominant hazard has been found within a 100 km distance and no hazards have been observed from a long distance as a controlling scenario from the analysis.