The 2017 Pohang earthquake (M_w 5.4) is the largest earthquake associated with fluid injection activities. We report new characteristics of the earthquake and propose a dislocation‐type model explaining previously reported observations. We identify fault geometry by relocating the hypocenters of 1,132 events that occurred during the first 3 months and then resolve their source regions as the northern, central, and southern patches, based on event groups with similar waveforms. The spatial features of these similar waveform groups, in addition to our obtained source mechanisms, indicate that oblique contraction is prevalent in the source region: Reverse faulting dominates the southern fault and the deeper part of the central fault; near‐parallel strike‐slip sense controls the northern fault and the shallower part of the central fault. Furthermore, we identify a migrating aftershock pattern that matches the fluid diffusion process along both sides of the northern and central faults. This observation suggests the interconnection of the two faults, allowing fluid transport, and implies mainshock coseismic movement along the fault intersection. The coseismic slip of the fault intersection can induce a fault‐valve process, which explains the aftershock migration pattern along the two intersecting faults. The proposed fault interaction accounts for the previously reported uplift between the two intersecting faults and successfully reproduces the non‐double‐couple mechanism of the mainshock. Our results raise the question of fluid‐faulting interactions in the aftershock seismicity of the Pohang earthquake, and the complex fault movement provides insight into the rupture process that allowed the Pohang earthquake runaway.

中文翻译：

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分区断层运动和余震触发：韩国浦项2017年Mw 5.4地震期间断层相互作用的证据

2017年浦项地震（M _w5.4）是与流体注入活动有关的最大地震。我们报告了地震的新特征，并提出了一种位错类型的模型来解释以前报道的观测结果。我们通过重新定位在前三个月发生的1,132个事件的震源来识别断层的几何形状，然后根据具有相似波形的事件组将其源区域解析为北部，中部和南部斑块。这些相似的波形群的空间特征，除了我们获得的震源机制外，还表明斜收缩在震源区中很普遍：逆断层主导着南部断层和中央断层的较深部分。接近平行的走滑感控制北部断裂和中央断裂的较浅部分。此外，我们确定了与北部和中央断裂两侧的流体扩散过程相匹配的迁移余震模式。该观察结果表明了两个断层的相互连接，允许流体运移，并暗示了沿断层相交处的主震同震运动。断层相交处的同震滑动会诱发断层-阀过程，这解释了沿两个相交断层的余震迁移模式。拟议的断层相互作用解释了先前报道的两个相交断层之间的隆升，并成功地再现了主震的非双耦合机制。我们的结果提出了浦项地震余震地震活动中流体断裂相互作用的问题，