A hybrid recurrence model and its implication on seismic hazard results

Abstract

Abstract To account for the effects of the characteristic earthquakes on an individual fault (segment), a renewal hybrid model is proposed for seismic hazard analysis and studied in depth. This model incorporates a renewal-time, characteristic-magnitude model for larger earthquakes with the conventional exponential-time, exponential-magnitude model for smaller earthquakes. Properties of important temporal and magnitude parameters are studied. The exact and the approximate (“first-event”) hazards estimated by this model are discussed. The approximate results are found sufficiently accurate for most engineering applications. These approximations can be obtained by making minor modifications to existing hazard analysis programs designed for traditional Poisson models. Hazard estimates of this model and other more complicated hybrid models, e.g., time- and slip-predictable models, are compared. For reasonable parameter values, the characteristic events are found to be the major contributor to seismic hazards in most cases, unless the source-site distance is very small. This effect is even stronger with a large elapsed time in a nonmemoryless interarrival time distribution. Based on previous findings of small values of the coefficients of variation in time and low correlations between the interarrival times and magnitudes among characteristic earthquakes, the proposed renewal hybrid model will produce hazard estimates close to those of more complicated non-Poissonian models.