The final size of an earthquake typically cannot be predicted from its ongoing seismic radiation. Expanding observations reveal distinct exceptions, such as slow earthquakes, injection-induced seismicity, and earthquake swarms, in which fault slip has an upper bound. A common thread among these anomalies is the diffusive migration of their active areas. Here, we report a unified scaling relation for these diffusional earthquakes. By tracking prolonged earthquake swarms in Northeast Japan, we constrained the time evolution of their active seismicity areas and cumulative seismic moments. Their moment-duration trajectories coincide with the final states documented for global swarms and induced seismicity across various scales. When plotted as seismic moment versus seismicity area, their trajectories collapse onto those of slow earthquakes, uniformly explained by a diffusional constant-slip model. This constant-slip scaling carves out a unique class of diffusional earthquakes, where the final available seismic energy is predetermined by slip distance.

翻译：地震的最终规模通常无法从其持续的地震辐射中预测。不断扩展的观测揭示了明显的例外情况，例如慢地震、注水诱发地震活动以及地震群，在这些事件中，断层滑动存在上限。这些异常现象的共同点是其活动区域的扩散性迁移。在此，我们报告了这些扩散性地震的统一标度关系。通过追踪日本东北地区的长期地震群，我们限定了其活跃地震活动区域和累积地震矩的时间演化。它们的矩-持续时间轨迹与全球不同尺度地震群和诱发地震活动记录的最终状态一致。当以地震矩与地震活动区域作图时，其轨迹与慢地震的轨迹重叠，并统一由扩散性的恒定滑动模型解释。这一恒定滑动标度关系刻画出一类独特的扩散性地震，其中最终可用的地震能量由滑移距离预先确定。