Comparison of characteristic and Gutenberg–Richter models for time–dependent M≥6.0 earthquake hazard in the Corinth gulf, Greece

Earthquake forecasts have always been a difficult task because they can be affected by uncertainty in terms of the most appropriate model and the involved parameter values. The application of two quite different models to the same seismogenic area was explored. The first belongs to the category of the renewal models, based on the characteristic earthquake hypothesis, the necessary ingredients of which being historical or paleoseismic recurrence times, and a fixed geometry for the faults. The hazard rate so obtained is then modified by the inclusion of a permanent effect due to the Coulomb static stress change caused by failure of neighbouring faults that occurred since the latest characteristic earthquake on the concerned fault. The second model consists of a very simple earthquake simulator, which can be described by parameters taken from two data input classes, fault slip rates and adoption of a Gutenberg–Richter magnitude–frequency distribution. This information is commonly available even if historical and paleoseismic recurrence data are lacking. The intention is to develop and assess a simulator that has a very limited parameter set, which has the benefit ofreducing and quantifying uncertainty. We apply both methods along the Corinth gulf extension zone, a place that is rich with observations of strong–earthquake recurrence behaviour, to assess their relative forecast applicability. We find that use of slip rate as a primary constraint allows the simulator to replicate the pattern of observed segmented rupture rates along the Corinth seismogenic zones. As they evolve through time, our rupture simulations preferentially fill slip gaps, enabling estimates of time–dependent segment recurrence. We conclude that very simple earthquake rupture simulations based on empirical data and fundamental earthquake laws can be useful forecast tools.