Subduction zones generate the largest earthquakes on Earth, yet their detailed structure, and its influence on seismic and aseismic slip, remains poorly understood. Geological studies of fossil subduction zones characterize the seismogenic interface as a 100 m–1 km thick zone^1,2,3 in which deformation occurs mostly on metres-thick faults^1,3,4,5,6. Conversely, seismological studies, with their larger spatial coverage and temporal resolution but lower spatial resolution, often image the seismogenic interface as a kilometres-wide band of seismicity⁷. Thus, how and when these metre-scale structures are active at the seismic-cycle timescale, and what influence they have on deformation is not known. Here we detect these metres-thick faults with seismicity and show their influence on afterslip propagation. Using a local three-dimensional velocity model and dense observations of more than 1,500 double-difference relocated earthquakes in Ecuador, we obtain an exceptionally detailed image of seismicity, showing that earthquakes occur sometimes on a single plane and sometimes on several metres-thick simultaneously active subparallel planes within the plate interface zone. This geometrical complexity affects afterslip propagation, demonstrating the influence of fault continuity and structure on slip at the seismogenic interface. Our findings can therefore help to create more realistic models of earthquake rupture, aseismic slip and earthquake hazard in subduction zones.

俯冲带产生了地球上最大的地震，但其详细结构及其对地震和地震滑移的影响仍然知之甚少。对化石俯冲带的地质研究将孕震界面描述为一个 100 m-1 km 厚的区域^1,2,3，其中变形主要发生在米厚的断层上^1,3,4,5,6。相反，地震学研究具有较大的空间覆盖范围和时间分辨率，但空间分辨率较低，通常将震源界面想象为千米宽的地震活动带⁷。因此，这些米级结构如何以及何时在地震周期时间尺度上活跃，以及它们对变形有什么影响尚不清楚。在这里，我们通过地震活动检测这些米厚的断层，并显示它们对后滑传播的影响。利用当地三维速度模型和对厄瓜多尔 1,500 多次双差重定位地震的密集观测，我们获得了异常详细的地震活动图像，显示地震有时发生在单个平面上，有时发生在几米厚的同时活动的地震上。板界面区域内的次平行平面。这种几何复杂性影响后滑传播，证明了断层连续性和结构对震源界面滑移的影响。因此，我们的研究结果有助于创建更真实的俯冲带地震破裂、地震滑移和地震灾害模型。