Evaluation and comparison of probabilistic and deterministic seismic hazard assessment: a case study of North-Eastern India

Abstract

Probabilistic and deterministic seismic hazard assessment (PSHA and DSHA) are distinct methodologies utilized for estimation of the seismic hazard at a specific site. PSHA provides a probabilistic estimate of the hazard that could occur at a site, over a certain period of time, considering all possible seismic sources in the vicinity, while DSHA provides a deterministic estimate of the hazard that could be experienced at the site, resulting from a particular earthquake scenario. Hence, one should be careful while comparing the outcomes from PSHA and DSHA, as they represent different approaches to seismic hazard assessment with divergent underlying assumptions and limitations. Failing to recognize these differences may result in a misinterpretation of seismic hazard. Therefore, an attempt is made in this study to obtain a more comprehensive understanding of seismic hazard and to appreciate the strengths and limitations of PSHA and DSHA. The seismic hazard computation is focused on the North-Eastern region of the Indian subcontinent. The PSHA results considering logic tree approach and GMPE rule, as reported by Gurjar and Basu [Gurjar and Basu in Pure Appl Geophys, 2022;Gurjar and Basu in Pure Appl Geophys, 2022;] are utilized for this purpose. DSHA is performed in this study, using a logic tree approach, and the weighted mean representation of hazard spectra from 50th percentile (median from GMPE) DSHA is compared with weighted mean and fractile (from distribution of the intensity measure) representation of UHS from PSHA at different return periods. Contour maps representing the weighted mean hazard are provided for soil site class B and two different time periods.