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arXiv 2602.06703physics.geo-ph
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潮汐触发慢地震的理论约束

Theoretical constraints on tidal triggering of slow earthquakes

Ecole Normale Supérieure, CNRS-UMR 8538, PSL Research University(巴黎高等师范学院);Bureau de Recherches Géologiques et Miniéres (BRGM)(法国地质矿产调查局);Department of Earth and Planetary Science, The University of Tokyo(东京大学地球行星科学系)

Yishuo Zhou, Ankit Gupta, Hideo Aochi, Alexandre Schubnel, Satoshi Ide, Pierpaolo Dubernet, Harsha S. Bhat

AI总结:

利用弹簧-滑块模型和速率-状态摩擦定律,研究潮汐应力对速度弱化稳定滑动断层的触发机制,发现小扰动可触发周期性或复杂滑移事件,触发行为由归一化周期和振幅控制。

摘要:

潮汐应力是由月球和太阳的引力驱动的全球性扰动。理解潮汐应力如何触发地震事件对于约束对小应力扰动敏感的构造环境至关重要。这里,我们采用具有速率-状态摩擦的弹簧-滑块模型,研究潮汐触发对刚度略超过临界刚度的速度弱化稳定滑动断层的影响。我们首先施加一个阶跃和一个有限持续时间的箱形法向应力扰动,以展示特定箱形持续时间下滑移速度的共振式放大。接下来,我们使用谐波扰动进行无量纲分析和数值模拟,以识别控制潮汐触发的关键参数及其允许范围。进一步使用物理可观测的量(包括辐射效率和潮汐相位)来表征触发的滑移事件。我们的结果表明,即使是小的应力扰动也能在稳定滑动断层上触发周期性以及时间上复杂的滑移事件。触发行为主要由归一化扰动周期和归一化扰动振幅控制。归一化周期的增加将事件时间从潮汐应力峰值转向应力率峰值,而归一化振幅的增加则促进从慢事件向快事件的转变。该框架有助于解释周期依赖的敏感性以及潮汐应力与最大滑移速度之间观测到的相位偏好。因此,观测与模型预测的潮汐相关模式之间的比较有助于约束界面的瞬时摩擦强度以及摩擦弱化的特征滑移距离。

英文摘要:

Tidal stress is a globally acting perturbation driven primarily by the gravitational forces of the Moon and the Sun. Understanding how tidal stresses can trigger seismic events is essential for constraining tectonic environments that are sensitive to small stress perturbations. Here, employing a spring-block model with rate-and-state friction, we investigate tidal triggering on velocity-weakening stable sliding faults with stiffness slightly exceeding the critical stiffness. We first apply a step and a boxcar with finite duration normal stress perturbation to demonstrate a resonance-like amplification of slip velocity for specific boxcar durations. Next, we perform nondimensional analyses and numerical simulations with harmonic perturbations to identify the key parameters controlling tidal triggering and their admissible ranges. Triggered slip events are further characterized using physically observable quantities, including radiation efficiency and tidal phase. Our results show that even small stress perturbations can trigger periodic as well as temporally complex slip events on stable sliding faults. The triggering behavior is primarily controlled by the normalized perturbation period and the normalized perturbation amplitude. An increase in the normalized period shifts event timing from the peak of tidal stress toward the peak of stress rate, whereas increasing the normalized amplitude promotes a transition from slow to fast events. This framework helps explain the period-dependent sensitivity and the observed phase preference between tidal stress and maximum slip velocity. Comparison between observed and model-predicted tidal correlation patterns may therefore help constrain the instantaneous frictional strength of the interface, as well as the characteristic slip distance for frictional weakening.

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