Fault Segmentation Pattern Controlled by Thickness of Brittle Crust

Abstract

AbstractDuring large earthquakes, seismic sources tend to split in several sub‐events that rupture neighboring fault patches called fault segments. The scaling of such segmentation plays a decisive role in earthquake rupture dynamics, especially for strike‐slip events. Using numerical modeling we demonstrate that when a pristine layer of brittle material is sheared, the first oblique Riedel fractures nucleate with a regular spacing that is controlled by the thickness of that layer. During later localization of the deformation, those initial fractures control the spatial structuration of the entire fault system. Analyzing the horizontal stress distribution in fault‐parallel direction for different ratios between inter‐Riedel distance and material thickness, we identify a threshold at 1.5, beyond which the stress switches from compressional to tensional and leads to the nucleation of a new Riedel fracture. Thus, the inter‐Riedel segment length appears to be controlled by the vertical distribution of stress along the fault.