Matthias Rosenau, Illia Horenko, Fabio Corbi, Michael Rudolf, Ralf Kornhuber, Onno Oncken

The size of great subduction megathrust earthquakes is controlled mainly by the number of adjacent asperities failing synchronously and the resulting rupture length. Here we investigate experimentally the long-term recurrence behavior of a pair of asperities coupled by quasi-static stress transfer over hundreds of seismic cycles. We statistically analyze long (c. 500 ka) time-series of M8-9 analogue earthquakes simulated using a seismotectonic scale model approach with two aims: First, to constrain probabilistic measures (frequency-size distribution, variability) useful for hazard assessment and, second, to relate them with geometric observables (coseismic slip pattern, locking pattern). We find that the number of synchronized failures (double events) relative to the number of individual failures (solo events) as well as the coefficient of variation of recurrence intervals scale with the logarithm of stress coupling between the asperities. Tighter packed asperities tend to recur more periodically while more distant asperities show clustering. The probability of synchronized failures is controlled to first order by geometrical relations (size and distance of asperities). The effects of rheological properties are evident but it remains to be explored to which extent they vary in nature and how sensitive the system is to those.