量化三维断层几何复杂性对慢地震和快地震的作用
Quantifying the Role of 3D Fault Geometry Complexities on Slow and Fast Earthquakes
AI总结：
通过三维准动态地震序列模拟，研究平行断层相互作用如何产生慢滑移事件和地震，发现仅几何复杂性就能通过牵引力异质性生成慢地震和快地震。
摘要：
慢滑移事件（SSEs）的传统模型过度简化了断层几何，尽管成像显示俯冲断层是分段且复杂的。我们使用三维准动态地震序列模拟，研究两个具有均匀速率弱化摩擦的平行断层（由分层矩阵加速）的相互作用如何控制滑移行为。出现了四种状态——周期性地震、SSEs与地震共存、仅SSEs以及复杂序列——而在相同摩擦条件下，单个平面断层只产生地震。我们通过相邻断层上空间均匀的单位应力降在目标断层上引起的最大库仑应力来量化相互作用。由于应力降已归一化，该度量仅取决于几何形状，与摩擦无关，从而可推广到任意断层系统。SSEs仅出现在中等断层相互作用强度下。在低相互作用强度下，系统产生规则的周期性地震。在高相互作用强度下，断层相互作用产生具有不规则复发和可变震级的复杂地震序列。模拟重现了观测到的矩-持续时间标度，并显示出对检测阈值的敏感性。这些结果表明，仅几何复杂性就能通过演化的牵引力异质性同时产生慢地震和快地震。
英文摘要：
Traditional models of slow slip events (SSEs) oversimplify fault geometry, although imaging shows subduction faults are segmented and complex. We examine how fault interactions control slip behavior using 3-D quasi-dynamic earthquake sequence simulations of two parallel faults with uniform rate-weakening friction accelerated by hierarchical matrices. Four regimes emerge-periodic earthquakes, coexisting SSEs and earthquakes, only SSEs, and complex sequences-whereas with the same friction condition a single planar fault produces only earthquakes. We quantify interaction using the maximum Coulomb stress induced on a target fault by a spatially uniform unit stress drop on a neighboring fault. Because the stress drop is normalized, the metric depends only on geometry and is independent of friction, allowing extension to arbitrary fault systems. SSEs occur only at intermediate fault interaction strengths. At low interaction strengths, the system produces regular, periodic earthquakes. At high interaction strengths, fault interactions generate complex earthquake sequences with irregular recurrence and variable magnitudes. Simulations reproduce observed moment-duration scaling and show sensitivity to detection thresholds. These results demonstrate geometric complexity alone generates both slow and fast earthquakes through evolving traction heterogeneity.
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