Linking Earthquake Magnitude-Frequency Statistics and Stress in Visco-Frictional Fault Zone Models

The ability to estimate the likelihood of given earthquake magnitudes is critical for seismic hazard assessment. Earthquake magnitude-recurrence statistics are empirically linked to stress, yet which fault-zone processes explain this link remains debated. We use numerical models to reproduce the interplay between viscous creep and frictional sliding of a fault-zone, for which inter-seismic locking becomes linked to stress. The models reproduce the empirical stress-dependent earthquake magnitude distribution observed in nature. Stress is related to the likelihood a fault section is near frictional failure, influencing likely rupture lengths. An analytical model is derived of a fault consisting of identical patches, each with a probability of inter-seismic locking. It reproduces a similar magnitude-recurrence relationship, which may therefore be caused by probabilistic clustering of locked fault patches. Contrasts in earthquake statistics between regions could therefore be explained by stress variation, which has future potential to further constrain statistical models of regional seismicity.