Comments on ‘Why is Probabilistic Seismic Hazard Analysis (PSHA) still used?’ by F. Mulargia, P.B. Stark and R.J. Geller

Abstract

Parsons et al. (2012), compared the characteristic and Gutenberg–Richter (G-R) distributions for time-dependent M ≥ 7.9 earthquake probability in the Nankai-Tokai subduction zone, Japan, a region for which historical information about several repeating strong earthquakes does exist. The purpose of their paper was to assess the possibility of making reasonable hazard assessments without requiring a characteristic model, and the conclusion was yes. In fact, they found that a simulator that imposes no physical geometric rupture barriers (meaning gaps or steps in the faults), can replicate the spatial proportion of fault segment ruptures evident within the studied area (within 95% confidence bounds). They concluded that the adoption of a G-R model can attain very similar matches to the historical catalog of the Nankai-Tokai zone, and suggested that very simple earthquake rupture simulations based on empirical data and fundamental earthquake laws could be useful forecast tools in information-poor settings.