Impact of Fault Heterogeneity on Fracture Energy

Despite the large number of observed earthquakes, the scaling of earthquake energy budget, particularly of the fracture energy, remains a subject of debate, as it is difficult to infer it through geological or seismological methods. Here, we explore the potential relationship between initial fault heterogeneity and fracture energy during rupture. Relying on concepts of wear analysis, we combine results of direct shear laboratory experiments involving interlocked rough surfaces and results of modeling in a framework of damage-breakage rheology. Our findings suggest that fracture energy per slip amount and fault area, normalized by the normal stress, increases with fault heterogeneity due to enhanced damage accumulation through shear. In faults exhibiting self-affine geometrical irregularities with a constant scaling exponent, we find that fracture energy scales with rupture size and amplitude of heterogeneity. However, this relationship may not hold if the self-affine nature of the fault is disrupted at some scale.