深浅地震活动分离揭示水库诱发与断层锁段并存
Juxtaposition of Shallow Reservoir-Triggered Seismicity and Deep Tectonic Locking in the Qiaojia-Dongchuan Seismic Gap
- 发现浅层高b值（1.0）为流体诱发地震，深层低b值（<0.8）显示断层锁段
- 20公里深度处应力积累速率高，表明该地震空区处于临界破裂状态
- 适用于大型水库-断层系统风险评估，尤其关注深部隐性应变累积
识别成熟地震空区的临界状态具有挑战性，尤其当人工应力扰动（如水库蓄水）叠加于构造加载时。本文基于世界第二大水电站所在地——巧家-东川地震空区的高分辨率密集台阵目录，揭示了明显的垂直解耦机制：浅层地震活动表现为高b值（1.0），指示流体驱动的水库诱发地震；而深层地震（20公里）则呈现‘锁段’特征，表现为低b值（小于0.8）和高库仑应力积累速率。进一步识别出复杂倾斜结构，暗示复合断层运动机制。应力积累计算表明，该地震空区处于临界状态，破裂潜力升高。研究发现，浅层人为地震可能掩盖深层构造应变的无声累积。这一解耦模型为全球水库-断层系统的地震风险评估提供了新框架。
原文摘要 · Abstract (English)
Identifying the critical state of mature seismic gaps is challenging, especially when anthropogenic stress perturbations, such as reservoir impoundment, superimpose on tectonic loading. Here, utilizing a high-resolution dense array catalog from the Qiaojia-Dongchuan seismic gap (hosting the second-largest hydropower station in the world), we reveal a distinct vertical decoupling mechanism. The shallow activities exhibit high b-values (1.0), indicative of fluid-driven reservoir-triggered seismicity. Conversely, deep seismicity (20 km) outlines a 'locked asperity' characterized by low b-values (less than 0.8) and high Coulomb stress accumulation rate. We further identify a complex dipping structure, suggesting compound fault kinematics. Additionally, the calculated stress accumulation suggests this seismic gap is in a critical state with elevated rupture potential. Our findings indicate that shallow induced seismicity can mask the silent accumulation of deep tectonic strain. This decoupling model provides a new framework for assessing seismic risks in reservoir-fault systems globally.
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