Testing of the Seismic Gap Hypothesis in a Model With Realistic Earthquake Statistics

Abstract

The seismic gap hypothesis states that fault regions where no large earthquake has recently occurred, are more prone than others to host the next large earthquake. It can lead to the idea of immunity after local disaster which, notwithstanding it sounds reasonable, it has been frequently rejected by objective testing. More generally, the estimate of the occurrence probability of the next big shock on the basis of the time delay from the last earthquake still represents a big challenge. The problem is that this issue cannot be addressed only on the basis of historical catalogs which contain too few well documented big shocks, and decades of future observations appear necessary. On the other hand, recent results have shown that important insights can be obtained from the spatial organization of aftershocks and its relationship to the mainshock slip profile. Here, we address this issue by monitoring the stress evolution together with the occurrence of big shocks and their aftershocks in a model where the fault is described as an elastic interface embedded in a ductile medium. The model reproduces all relevant statistical features of earthquake occurrence and allows us to perform accurate testing of the seismic gap hypothesis and its consequences, particularly on the side of aftershock spatial patterns. We show that large earthquakes do not regularly repeat in time, but it is possible to achieve insights on the time until the next big shock from the percentage of aftershocks occurring inside the mainshock slip contour.