Dynamics of non-self-similar earthquakes illuminated by a controlled fault asperity

Abstract

Abstract Most ordinary earthquakes follow self-similar scaling, where source duration scales with the cube root of seismic moment. However, some earthquake clusters show non-self-similar scaling, in which source duration remains nearly constant regardless of seismic moment. Their source mechanisms, previously proposed to involve fixed source dimensions with variable stress drop or accelerating rupture velocity, are not fully validated due to uncertainties in estimating source properties, often caused by observational biases such as path effects. Here, we present a dynamic rupture model for non-self-similar earthquakes based on laboratory experiments conducted on a meter-scale fault with size- and shape-controlled gouge patch sources. By carefully applying corrections for instrumental response, sensor coupling, and attenuation to acoustic emission waveforms, we reliably constrain the source parameters of gouge patch events and identify non-self-similar scaling across magnitudes from M w -7.3 to -6.0. We further develop a dynamic rupture model that quantitatively explains the observed source parameters by incorporating a fixed source-patch size, variable stress drop within the patch, and self-healing friction. This modeling framework complements previously proposed models and expands the range of tectonic conditions under which non-self-similar earthquakes may occur.