Summary

This study investigates various types of seismicity changes that occurred in several regions in and around the Tohoku District, prior to the 2011 M9.0 Tohoku–Oki earthquake. In particular, we focus on the seismicity anomalies that were revealed not only in inland local areas but also in a wide area for several years before the 2008 M7.2 earthquake in the inland Tohoku District. We reconsider these seismicity anomalies in nearly identical regions, which persisted in the extended period up until the M9 mega event. This suggests that the stress changes due to transient slow slips on the Pacific Plate boundary are more likely to be the cause of the wider seismicity changes than the slips beneath the inland earthquake. To confirm the significance, we use the two-stage stationary epidemic-type aftershock sequence model and explore the relationship between seismicity changes and stress rate changes due to slow slip by means of global navigation satellite system geodetic observations.

中文翻译：

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2011年东北冲木地震前的广域地震活动异常

概要

这项研究调查了在2011年M 9.0级东北冲木地震之前，东北地区及其周边多个地区发生的各种类型的地震活动变化。特别是，我们着眼于不仅在内陆地区而且在2008 M内陆东北地区发生7.2级地震。我们重新考虑了几乎相同区域的地震活动异常，这些异常现象一直持续到M9特大事件。这表明，与内陆地震下方的滑动相比，太平洋板块边界上瞬态缓慢滑动引起的应力变化更可能是造成地震活动性变化更大的原因。为了证实其重要性，我们使用了两阶段平稳流行型余震序列模型，并通过全球导航卫星系统的大地观测，探索了地震活动性和慢滑引起的应力率变化之间的关系。