Probabilistic Seismic Hazard Assessment for Jamaica

Abstract

A probabilistic seismic hazard analysis was performed to generate seismic hazard maps for Jamaica. The analysis was then conducted using a standard logic-tree approach that allowed systematically taking into account the model-based (i.e., epistemic) uncertainty and its influence on the computed ground motion parameters. Hazard computations have been performed using a grid of sites with a space of 0.05 degrees. Two different computation methodologies have been adopted: the standard approach based on the definition of appropriate seismogenic sources and the zone-free approach, which overcomes the ambiguities related with the definition of the seismic sources solely reflecting the characteristics of the earthquake catalogue. A comprehensive and updated earthquake catalogue for Jamaica has been compiled for the years 1551-2010 and new empirical relationships amongst magnitudes MW-MS and MW-mb have been developed for the region. Uniform hazard spectra and their uncertainty have been calculated for the horizontal component of ground motion for rock site conditions and five return periods (95, 475, 975, 2,475 and 4,975 years) and spectral accelerations for 34 structural periods ranging from 0 to 3 s, and 5% of critical damping. The spectral accelerations have been calculated to allow the definition of seismic hazard in Jamaica according to the International Building Code 2012. The disaggregation analysis for Kingston Metropolitan Area suggests that the magnitude-distance pair that contributes most to the hazard corresponds to events with M 7.8 and M 7.0 in the Enriquillo Plantain Garden Fault and the Jamaican Faults at a distance of 28 km and 18 km for short and long period structures respectively corresponding to 2,475 years return period. However, for long period structures, a substantial contribution is found for a M 8.2 at a distance of 198 km in the Oriente Fault Zone.