Abstract Tectonically active fault networks are often inter-connected, but in the case of injection-induced seismicity, prior knowledge of fault architecture tends to be severely limited. In most cases, reactivated faults due to fluid injection are inferred, after-the-fact, by the spatial distribution of induced-seismicity hypocenters; such reliance on post-injection seismicity impedes any pre-operational risk analysis, as well as development of a more holistic understanding of fault-system models. By combining high-resolution, depth-migrated 3-D seismic data with a new focal-depth estimation method that reduces spatial uncertainty of hypocenters, this study pinpoints microearthquake fault activation within a buried thrust belt in the Montney Formation in western Canada (British Columbia). During hydraulic-fracturing operations, rupture nucleation occurred on seismically imaged thrust ramps that cut through the Debolt Formation, a massive carbonate layer that underlies the stimulated zone. High-resolution seismic images reveal transverse structures, interpreted as basement-controlled fold hinges or tear faults that transferred displacement between thrust faults during Late Cretaceous - Paleogene compressional shortening. The spatio-temporal pattern of induced seismicity suggests that these transverse structures provide permeable pathways for aseismic pore-pressure diffusion, thus connecting distinct thrust faults and enabling earthquake triggering on a timescale of days and at distances of up to 2 km from the injection wells. Inferred relationships highlight how the fault system is connected, including apparent stress concentrations at the intersections of transverse structures and orogen-parallel thrust ramps.

中文翻译：

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水力压裂过程中激活的隐埋推力带的解剖

摘要 构造活动断层网络通常相互连接，但在注入诱发地震活动的情况下，断层结构的先验知识往往受到严重限制。在大多数情况下，事后通过诱发地震震源的空间分布推断出由于流体注入而重新激活的断层；这种对注入后地震活动的依赖阻碍了任何操作前风险分析以及对断层系统模型的更全面理解的发展。通过将高分辨率、深度偏移的 3-D 地震数据与降低震源空间不确定性的新震源深度估计方法相结合，本研究精确定位了加拿大西部（不列颠哥伦比亚省）Montney 地层埋藏冲断带内的微地震断层激活）。在水力压裂作业中，破裂成核发生在地震成像的推力斜坡上，该斜坡穿过 Debolt 地层，这是一个位于受激层下方的巨大碳酸盐岩层。高分辨率地震图像揭示了横向结构，解释为基底控制的褶皱铰链或撕裂断层，在晚白垩世 - 古近纪压缩缩短期间转移逆冲断层之间的位移。诱发地震活动的时空模式表明，这些横向结构为抗震孔隙压力扩散提供了可渗透的途径，从而连接了不同的逆冲断层，并能够在数天的时间尺度上和距注入井长达 2 公里的距离触发地震。推断的关系突出了故障系统是如何连接的，