Physics-based probabilistic seismic hazard assessment using synthetic ground motions: application to the stable continental region of India

Attaining explicit hazard estimates is a challenging task for data sparse regions such as the Peninsular India. Physics based probabilistic seismic hazard analysis (Pb-PSHA) has gained momentum in recent years as a viable solution to this issue. While performing a site-specific analysis in data-sparse regions, instead of incorporating ground motion models (GMMs) from other regions in the hazard methodology, the Pb-PSHA involves obtaining physics-based numerical simulations. In the present study, Pb-PSHA is carried out for the entire southern Peninsular India, with a detailed demonstration for the Kalpakkam site, Tamilnadu. Due to absence of any data on local fault characteristics and past rupture models, simulations are derived using the spectral element method, for several source rupture scenarios. Further, the stochastic seismological model is used to simulate for high frequency (1-100 Hz) ensemble ground motions. Broadband ground motions are then obtained by combining the results from the deterministic model i.e., low frequency (0.01-1 Hz) simulations and the stochastic model. Further, PSHA based on elliptical gridded seismicity is carried out to obtain hazard curves for spectral accelerations. The ensuing uniform hazard response spectra are compared against the outcome of traditional PSHA involving a global GMM. The results indicate that the PGA values obtained from the Pb-PSHA are slightly higher than that of the global GMM-based PSHA.