Reconsidering earthquake scaling

The relationship (scaling) between scalar moment, M₀, and duration, T, potentially provides key constraints on the physics governing fault slip. The prevailing interpretation of M₀-T observations proposes different scaling for fast (earthquakes) and slow (mostly aseismic) slip populations and thus fundamentally different driving mechanisms. We show that a single model of slip events within bounded slip zones may explain nearly all fast and slow slip M₀-T observations, and both slip populations have a change in scaling, where the slip area growth changes from 2-D when too small to sense the boundaries to 1-D when large enough to be bounded. We present new fast and slow slip M₀-T observations that sample the change in scaling in each population, which are consistent with our interpretation. We suggest that a continuous but bimodal distribution of slip modes exists and M₀-T observations alone may not imply a fundamental difference between fast and slow slip.