耦合瞬态过程控制板内地震群演化：来自2019-2020年帕尔加尔序列的启示
Coupled Transient Processes Govern Intraplate Earthquake Swarm Evolution: Insights from the 2019-2020 Palghar Sequence
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中文总结 AI 辅助
该研究以2019-2020年帕尔加尔板内地震群为对象，结合高分辨率地震目录等数据，发现其演化由流体辅助变形与瞬态应力转移耦合控制，无法用单一端元模型解释，为研究稳定大陆地壳地震过程提供了新视角。
中文摘要 AI 辅助
地震群为研究断层对瞬态扰动的响应提供了天然窗口，然而其驱动过程通常用流体驱动和无震滑动驱动这两个端元模型来解释。板内地震群为检验这些模型提供了独特环境，因为低长期构造载荷会提高断层对瞬态非构造强迫的敏感性。我们利用机器学习增强的目录，其中包含来自印度西部2019-2020年帕尔加尔地震群的约50000次地震，来检验该端元框架。高分辨率重定位结合矩张量解，揭示了花岗岩基底中的两条浅正断层，地震活动从西断层依次迁移至东断层，随后扩展至中间的损伤带。尽管该地震群整体呈现类扩散扩展特征，但重定位后的地震活动显示出一条持续存在的、深度约5公里的局部地震活动带，且多次出现的迁移前沿有时传播速度快于仅由流体扩散预期的速度。这些间歇性事件的速度-持续时间标度同时跨越流体驱动和慢滑动驱动的两种机制。地震群持续期间的断层依次激活及不同迁移方式表明，其动力学无法用任何一种端元机制单独解释。相反，帕尔加尔地震群是通过相互作用断层网络内的流体辅助变形与瞬态应力转移耦合演化的，迁移事件与无震变形一致。这些观测结果表明，高分辨率目录可解析隐藏在看似扩散型地震群行为中的瞬态过程。更广泛而言，板内地震群为研究稳定大陆地壳中耦合瞬态过程如何控制地震触发及断层相互作用提供了强大的天然实验室。
英文摘要
Earthquake swarms provide a natural window into fault response to transient perturbations, yet their driving processes are commonly interpreted using fluid-driven and aseismic-slip-driven end-member models. Intraplate swarms offer a unique setting to test these models because low secular tectonic loading heightens the sensitivity of faults to transient, non-tectonic forcing. We use a machine-learning-enhanced catalog of $\sim$50,000 earthquakes from the 2019--2020 Palghar earthquake swarm in western India to test this end-member framework. High-resolution relocations, together with moment tensor solutions, reveal two shallow normal faults in a granitic basement, with seismicity sequentially migrating from the western to the eastern fault before expanding into the intervening damage zone. Although the swarm exhibits an overall diffusion-like expansion, the relocated seismicity reveals a persistent $\sim$5-km-deep localized seismicity band and repeated migration fronts sometimes propagating faster than expected from fluid diffusion alone. The velocity--duration scalings of these intermittent episodes span both fluid- and slow-slip-driven regimes. Sequential fault activation and contrasting migration styles throughout the swarm duration reveal dynamics that cannot be explained by either end-member mechanism alone. Instead, the Palghar swarm evolved through coupled fluid-assisted deformation and transient stress transfer within an interacting fault network, with migration episodes consistent with aseismic deformation. These observations reveal that high-resolution catalogs can disentangle transient processes hidden within apparently diffusive swarm behavior. More broadly, intraplate earthquake swarms provide powerful natural laboratories for resolving how coupled transient processes govern earthquake triggering and fault interaction in stable continental crust.
