Continental normal fault earthquakes have been reported to have smaller maximum magnitudes (M_max) than continental earthquakes with other fault geometries. This difference has significant implications for understanding seismic hazards in extensional regions. Using the Global Centroid Moment Tensor (GCMT) catalog, we examine how M_max varies with fault geometry in continental regions, whether these trends are robust, and potential physical reasons for the smaller magnitudes of continental normal fault earthquakes.

We find that the largest continental normal fault earthquakes are in the low M_w 7 range whereas other fault geometries can reach ~M_w 8. The continental normal fault earthquake magnitude-frequency distribution has a lower corner magnitude (a parameterization of M_max) than other fault geometries. The observed smaller continental normal fault M_max is not an artifact of classification criteria or catalog length. Probability calculations indicate that the GCMT catalog is long enough to capture differences in M_max due to fault geometry. Additionally, our analysis indicates that neither fault length nor width is limiting the size of continental normal fault earthquakes. Fault complexity can limit rupture extent, but it is likely not the primary reason for the smaller continental normal fault M_max.

Rather, lithosphere yield stress (strength) appears to be the main factor controlling M_max. In extension, lithosphere is weaker, failing at lower yield stresses than in compression. Although this yield stress difference is consistent with smaller continental normal fault earthquakes, it appears inconsistent with the occurrence of large oceanic normal fault earthquakes. However, the largest oceanic normal fault earthquakes occur near subduction zones where the lithosphere is bending. Laboratory studies indicate that bending lithosphere likely has a higher yield stress than lithosphere in pure extension, which may allow for larger oceanic normal fault earthquakes. Therefore, yield stress—rather than fault geometry alone—appears to be the key factor limiting an earthquake's maximum magnitude.

据报道，大陆正常断层地震的最大震级（M _max）比其他断层几何的大陆地震小。这种差异对于理解延伸区域的地震危害具有重大意义。使用全球质心矩张量（GCMT）目录，我们检查了M _max如何随大陆地区的断层几何形状变化，这些趋势是否稳健，以及潜在的物理原因，导致大陆正常断层地震的幅度较小。

我们发现最大的大陆正断层地震在M _w 7的低范围内，而其他断层的几何形状可以达到〜M _w 8。大陆正断层地震的幅值-频率分布的拐角震级（M _max的参数化）比其他断层几何。观测到的较小的大陆法向断层M _max不是分类标准或目录长度的假象。概率计算表明，GCMT目录足够长，可以捕获M _max中的差异由于故障的几何形状。此外，我们的分析表明，断层的长度和宽度都没有限制大陆正常断层地震的大小。断层的复杂性可以限制破裂的程度，但可能不是大陆法向断层M _max较小的主要原因。

相反，岩石圈屈服应力（强度）似乎是控制M _max的主要因素。延伸而言，岩石圈较弱，其屈服应力低于压缩应力。尽管该屈服应力差与较小的大陆正断层地震一致，但似乎与大洋正断层地震的发生不一致。但是，最大的海洋正断层地震发生在岩石圈弯曲的俯冲带附近。实验室研究表明，在纯伸展方面，弯曲的岩石圈可能比岩石圈具有更高的屈服应力，这可能导致更大的海洋正断层地震。因此，屈服应力（而不是单独的断层几何）似乎是限制地震最大震级的关键因素。