Application of time-independent and time-dependent occurrence models on the seismic hazard estimations in the Marmara region, Turkey

Abstract:

We show the effect of time-independent and time-dependent occurrence models on the seismic hazard estimations. The time-dependence is introduced by 1) the Brownian Passage Time (BPT) probability model that is based on a simple physical model of the earthquake cycle, and 2) the fusion of the BPT renewal model with a physical model that considers the earthquake probability perturbation for interacting faults by static Coulomb stress changes We treat the uncertainties in the fault parameters (e.g. slip rate, characteristic magnitude and aperiodicity) of the statistical distribution associated to each examined fault source by a Monte Carlo technique. For a comparison among the results obtained from three different models, we give the probabilities of occurrence of earthquakes Mw > 6.5 for individual fault sources in the Marmara region, over the future 5-10-30 and 50 years, starting on January 1, 2013, considering the 10^th, 50^th and 90^th percentiles of the Monte Carlo distribution.

In order to evaluate the impact of the earthquake probability models to ground motion hazard we attempt to calculate the fault-based probabilistic seismic hazard maps (PSHA) of mean Peak Ground Acceleration (PGA) having 10% probability of exceedance in 50 years on rock site condition. We adopted only one Ground Motion Prediction Equation (GMPE) for the active shallow crustal region for assessing the ground shaking hazard in the Marmara region.

We observed that the impact of the different occurrence models on the seismic hazard estimate of selected sites is quite high: the hazard may increase by more than 70% or decrease by as much as 70%, depending on the applied model in the selected sites. This difference mostly depends on the time elapsed after the latest major earthquake on a specific fault. We demonstrate that the estimated average recurrence time and the associated magnitude, together with the elapsed time, are crucial parameters in the earthquake probability calculations.