Faults are rarely completely smooth, with topographic undulations coming from the distribution of asperities along the fault surface. Understanding the effects of fault surface topography on fault strength and earthquake source properties has been limited due to a lack of in situ observations in the field. Here we use simulated earthquake cycles on metre-scale laboratory faults to show the effects of the degree of fault topographic heterogeneity, especially on macroscopic peak strength represented by the shear force required to commence macroscopic failure. Our results demonstrate that the less heterogeneous fault is weaker, due to its lower macroscopic peak strength, and produces a larger stress drop on average than the more heterogeneous fault. Rupture along the less heterogeneous fault tends to propagate at subshear speed while the more heterogeneous fault accommodates a wider range of rupture speeds, including slow slip and supershear rupture. These results reveal how fault topographic heterogeneity affects macroscopic peak strength at rupture initiation and stress drop during rupture propagation, which has important implications for understanding natural faults and earthquakes.

断层很少是完全光滑的，断层表面的粗糙分布导致地形起伏。由于缺乏现场观测，了解断层表面地形对断层强度和震源特性的影响一直受到限制。在这里，我们使用米级实验室断层上的模拟地震周期来显示断层地形非均质性程度的影响，特别是对宏观峰值强度的影响，该峰值强度由开始宏观破坏所需的剪切力表示。我们的结果表明，由于其较低的宏观峰值强度，异质性较小的断层较弱，并且平均产生比异质性较大的断层更大的应力降。沿着不均匀断层的破裂倾向于以亚剪切速度传播，而更不均匀的断层适应更宽范围的破裂速度，包括慢滑动和超剪切破裂。这些结果揭示了断层地形的非均质性如何影响破裂起始时的宏观峰值强度和破裂传播过程中的应力降，这对于理解天然断层和地震具有重要意义。