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, where 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, the trajectories of swarms and injection-induced seismicity collapse onto those of slow earthquakes, uniformly explained by a diffusional constant-slip model. The constant-slip scaling of diffusional earthquakes and the constant-stress-drop scaling of ordinary earthquakes mark a bimodal predictability in seismogenesis.

翻译：地震的最终震级通常无法从其持续的地震辐射中预测。越来越多的观测揭示了显著的例外情况，例如慢地震、注水诱发地震和地震群，这些情况下断层滑移存在上限。这些异常现象的共性在于其活跃区域的扩散性迁移。本文报告了这些扩散型地震的统一标度关系。通过追踪日本东北部的长期地震群，我们约束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范围内不同尺度的地震群和诱发地震记录的最终状态相吻合。当以地震矩对地震活动区域作图时，地震群和注水诱发地震的轨迹与慢地震的轨迹重合，并可由扩散恒定滑移模型统一解释。扩散型地震的恒定滑移标度和普通地震的恒定应力降标度，标志着地震成因中的双峰可预测性。