DETERMINISTIC VS. PROBABILISTIC SEISMIC HAZARD ASSESSMENT: AN EXAGGERATED AND OBSTRUCTIVE DICHOTOMY

Abstract

Deterministic and probabilistic seismic hazard assessment are frequently represented as irreconcilably different approaches to the problem of calculating earthquake ground motions for design, each method fervently defended by its proponents. This situation often gives the impression that the selection of either a deterministic or a probabilistic approach is the most fundamental choice in performing a seismic hazard assessment. The dichotomy between the two approaches is not as pronounced as often implied and there are many examples of hazard assessments combining elements of both methods. Insistence on the fundamental division between the deterministic and probabilistic approaches is an obstacle to the development of the most appropriate method of assessment in a particular case. It is neither possible nor useful to establish an approach to seismic hazard assessment that will be the ideal tool for all situations. The approach in each study should be chosen according to the nature of the project and also be calibrated to the seismicity of the region under study, including the quantity and quality of the data available to characterise the seismicity. Seismic hazard assessment should continue to evolve, unfettered by almost ideological allegiance to particular approaches, with the understanding of earthquake processes.