In subduction zones, slow slip events (SSEs) have been observed in the portion deeper than the downdip edge of seismogenic zone. However, since it is far offshore from geodetic networks on land, shallow SSEs near the trench axis are hardly observed. Despite of less quantitative than seafloor geodetic observations, a method for inferring the shallow SSEs based on seismic quiescence was presented in this study. Unusual decrease in occurrence rate of M ≥ 5.0 earthquakes was found in the southwestern Kurile Islands. The occurrence rate was ∼1.3 events/year between 1977 and around 2004 and no earthquake was observed during 16 years after 2004. The spatial pattern of the seismic quiescence can be explained qualitatively by the Coulomb failure stress change due to shallow SSE and its fault plane is on the upper boundary of the subducting Pacific plate in the focal area of the 1975 tsunami earthquake.

中文翻译：

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从不寻常的长期地震静止推断出 1975 年千岛海啸地震震源区的慢滑移事件

在俯冲带中，在比地震带下倾边缘更深的部分观察到慢滑移事件（SSE）。然而，由于它远离陆地上的大地测量网络，因此很难观察到海沟轴附近的浅层SSE。尽管定量程度低于海底大地测量观测，但本研究提出了一种基于地震静止推断浅层 SSE 的方法。西南千岛群岛5.0级以上地震发生率异常下降。1977年至2004年左右，发生率约为每年1.3次，2004年之后的16年里没有观测到地震。