Aftershocks are a fundamental characteristic of seismicity, and their generation mechanism is mainly characterized by two physical models, stress transfer from large earthquakes and afterslip-induced stress loading. However, the contribution of each mechanism to aftershock generation remains unclear. Here we investigate the spatiotemporal variations in aftershock activity following the 2011 Tohoku-Oki earthquake by applying the Hierarchical Space–Time Epidemic-Type Aftershock Sequence (HIST-ETAS) model to the decade of recorded seismicity since the mainshock. Using the estimated HIST-ETAS model, we categorize the aftershocks into background earthquakes (which are caused by aseismic phenomena) and triggered earthquakes (which are caused by earthquake-to-earthquake interactions). Most of the earthquakes that occurred updip of the large coseismic slip zone along the Japan Trench are triggered earthquakes, consistent with the lack of afterslip in this area. Conversely, background earthquakes are the predominant earthquake type in the long-term downdip of the large coseismic slip zone, and they positively correlate with the afterslip evolution. Our results suggest the importance of combining these two end-member aftershock generation models to explain aftershock activity and thus provide new insights into the relationship between afterslip and spatiotemporal aftershock distribution. Our classifications may also contribute to the monitoring of afterslip in a given region that hosts a large earthquake, particularly where geodetic observation networks are too sparse to evaluate afterslip evolution.

余震是地震活动的基本特征，其产生机制主要有大震应力传递和后滑应力加载两种物理模型。然而，每种机制对余震产生的贡献仍不清楚。在这里，我们通过将分层时空流行型余震序列 (HIST-ETAS) 模型应用于自主震以来有记录的十年地震活动，研究了 2011 年东北冲地震后余震活动的时空变化。使用估计的 HIST-ETAS 模型，我们将余震分为背景地震（由地震现象引起）和触发地震（由地震与地震相互作用引起）。大多数发生在日本海沟大型同震滑移带上倾的地震都是触发地震，这与该地区缺乏后滑一致。相反，背景地震是大同震滑移带长期下倾的主要地震类型，与后滑演化呈正相关。我们的结果表明，结合这两种端元余震生成模型来解释余震活动的重要性，从而为余滑与余震时空分布之间的关系提供新的见解。我们的分类还可能有助于监测发生大地震的给定区域的后滑，特别是在大地测量观测网络太稀疏而无法评估后滑演化的地方。

余震是地震活动的基本特征，其产生机制主要有大震应力传递和后滑应力加载两种物理模型。然而，每种机制对余震产生的贡献仍不清楚。在这里，我们通过将分层时空流行型余震序列 (HIST-ETAS) 模型应用于自主震以来有记录的十年地震活动，研究了 2011 年东北冲地震后余震活动的时空变化。使用估计的 HIST-ETAS 模型，我们将余震分为背景地震（由地震现象引起）和触发地震（由地震与地震相互作用引起）。大多数发生在日本海沟大型同震滑移带上倾的地震都是触发地震，这与该地区缺乏后滑一致。相反，背景地震是大同震滑移带长期下倾的主要地震类型，与后滑演化呈正相关。我们的结果表明，结合这两种端元余震生成模型来解释余震活动的重要性，从而为余滑与余震时空分布之间的关系提供新的见解。我们的分类还可能有助于监测发生大地震的给定区域的后滑，特别是在大地测量观测网络太稀疏而无法评估后滑演化的地方。