The Predictability of Large Earthquakes: Evidence from an Analogue Model of Earthquake Rupture

The recurrence behaviour of large earthquakes, in several tectonic settings, has been explained by simple models of stress accumulation and release which assume that the fault stress state is solely a function of the far-field tectonic strain rate. However, the limited dataset of large event recurrence intervals has been a major obstacle to the verification of these and other models. We present the results from a simple analogue model of earthquake rupture and stick-slip which displays power-law frequency-size statistics and involves many cycles of large events. We show that, despite the macroscopic homogeneity of the model, large events do not conform to simple deterministic time- or slip-predictable patterns. However, when the recurrence intervals for large events are divided by the median recurrence interval, the normalized data are composed of two distinct lognormally distributed populations. One population is characterized by events which are strongly clustered in time with relatively short recurrence intervals and low moment release, the other by events which are weakly clustered in time with median-sized recurrence intervals. It is suggested that the long-term recurrence behaviour of large earthquakes, whilst being non-deterministic, may be modelled by a well-defined statistical distribution of recurrence intervals.