Earthquakes occur within complex fault zones containing numerous intersecting fault strands. This complexity poses a computational challenge for rupture models, which typically simplify fault structure to a small number of rough fault surfaces, with all other deformation assumed to be off-fault viscoplastic deformation. In such models, high-frequency ground motions originate solely from frictionally mediated, heterogeneous slip on a small number of potentially rough fault surfaces or from off-fault viscoplastic deformation. Alternative explanations for high-frequency ground motion generation that can account for a larger number of fault surfaces remain difficult to assess. Here, we evaluate the efficacy of a recently proposed stochastic impact model in which high-frequency ground motion is caused by elastic impacts of structures within a complex fault zone. Impacts are envisioned to occur in response to fault motion in the presence of geometrical incompatibilities, which promotes transfer of slip onto different fault strands on timescales mediated by elasticity. We investigate the role of a complex fault zone for high-frequency ground motion by comparing the underlying assumptions and resulting predictions of impact and rough fault frictional models. Relative to rough fault frictional models, impact models are characterized by deformation timescales and corner frequencies that are set by elasticity rather than viscoplasticity, relatively angular rather than smoothly varying fault roughness geometries, high-frequency radiation patterns that are more isotropic, and higher P/S radiated energies. We outline ways to discriminate whether impact or rough fault frictional models are more likely to explain observations of high-frequency ground motions.

中文翻译：

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复杂断层带中高频辐射的冲击与摩擦地震模型

地震发生在包含许多相交断层链的复杂断层带内。这种复杂性给破裂模型带来了计算挑战，破裂模型通常将断层结构简化为少量粗糙的断层表面，所有其他变形假定为断层外粘塑性变形。在这样的模型中，高频地面运动仅源自摩擦介导的、少量潜在粗糙断层表面上的异质滑动或断层外的粘塑性变形。可以解释大量断层表面的高频地震动产生的替代解释仍然难以评估。这里，我们评估了最近提出的随机冲击模型的有效性，其中高频地震动是由复杂断层带内结构的弹性冲击引起的。预计在几何不兼容的情况下，响应于断层运动而发生影响，这会促进滑动在由弹性介导的时间尺度上转移到不同的断层链上。我们通过比较影响和粗糙断层摩擦模型的基本假设和结果预测来研究复杂断层带对高频地震动的作用。相对于粗糙断层摩擦模型，冲击模型的特点是变形时间尺度和角频率由弹性而不是粘塑性设置，相对角度而不是平滑变化的断层粗糙度几何形状，P / S辐射能量。我们概述了区分撞击模型还是粗糙断层摩擦模型更可能解释高频地面运动观测的方法。