Abstract. It is well-established that the post-seismic slip results from the combined contribution of seismic slip and aseismic slip. However, the partitioning between these two modes of slip remains unclear due to the difficulty to infer detailed and robust descriptions of how both evolve in space and time. This is particularly true just after a mainshock when both processes are expected to be the strongest. Using state-of-the-art sub-daily processing of GNSS data, along with dense catalogs of aftershocks obtained from template-matching techniques, we unravel the spatiotemporal evolution of post-seismic slip and aftershocks over the first 12 hours following the 2015 M_w8.3 Illapel, Chile, earthquake. We show that the very early post-seismic activity occurs over two regions with distinct behaviors. To the north, post-seismic slip appears to be purely aseismic and precedes the occurrence of late aftershocks. To the south, aftershocks are the primary cause of the post-seismic slip. We suggest that this difference in behavior could be inferred only few hours after the mainshock, and thus could contribute to a more data-driven forecasts of long-term aftershocks.

中文翻译：

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双峰摩擦行为很早就确定在2015年M的震后阶段_W¯¯ 8.3伊亚佩尔，智利，地震

摘要。公认的是，地震后滑动是由地震滑动和地震滑动的共同贡献引起的。然而，由于难以推断出两者在空间和时间上如何演变，因此很难对这两种滑动方式之间的划分进行不清楚。尤其是在主震发生后，这两个过程都将是最强大的。利用最新的GNSS次日处理，以及通过模板匹配技术获得的余震密集目录，我们揭示了2015 M之后的前12小时地震后滑动和余震的时空演变_w8.3智利伊拉佩尔地震。我们表明，非常早期的地震后活动发生在两个具有不同行为的区域。在北部，地震后的滑动似乎是纯粹的地震，并且早于余震的发生。在南部，余震是地震后滑动的主要原因。我们建议，可以在主震发生后仅几个小时就推断出这种行为上的差异，从而有助于以数据为依据的对长期余震的预测。