The Lesser Antilles subduction zone is a challenging region when it comes to unraveling its seismogenic behavior. Over the last century, the subduction megathrust has been seismically quiet, with no large thrust event recorded, which raises the question whether this subduction zone is able to produce large interplate earthquakes or not. However, two historical earthquakes in the 19th century, a M 7–8 in 1839 and M 7.5–8.5 in 1843, are proposed to have occurred along the subduction megathrust, although no direct evidence exists. Here we provide a new assessment of interseismic coupling for the Lesser Antilles subduction zone, based on updated Global Positioning System (GPS) velocities and the latest models of the slab geometry and elastic crustal structure. We use a Bayesian approach, allowing us to explore the entire range of plausible models and to provide realistic estimates of interseismic coupling and associated uncertainties. We find low to very low coupling along the entire plate interface, including in the proposed rupture areas of the 1839 and 1843 events, where the sensitivity of our model is high. While a further understanding of temporal variations in interseismic coupling needs to be addressed in future studies, our results indicate that the Lesser Antilles subduction zone is uncoupled, which challenges the idea that the 1839 and 1843 earthquakes were thrust events. The updated GPS velocities of this work now also reveal a small, but detectable amount of along‐arc extension, consistent with geological observations of active normal faulting within the arc.

中文翻译：

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沿安的列斯群岛小弧推断间震耦合：贝叶斯方法

小安提勒斯俯冲带是一个有挑战性的地区，要弄清它的地震成因。在上个世纪，俯冲巨推力一直处于地震平静状态，没有记录到大的推力事件，这引发了一个问题，即该俯冲带是否能够产生大的板间地震。然而，尽管没有直接的证据，但建议在俯冲巨推力作用下发生过两次19世纪的地震，即1839年的M 7-8和1843年的M 7.5-8.5。在此，我们根据更新的全球定位系统（GPS）速度以及平板几何形状和弹性地壳结构的最新模型，为小安的列斯群岛的俯冲带提供了地震耦合的新评估。我们使用贝叶斯方法 使我们能够探索所有可能的模型，并提供地震耦合和相关不确定性的现实估计。我们在整个板块界面上发现了从低到极低的耦合，包括在1839年和1843年事件的建议破裂区域中，我们的模型敏感性很高。尽管在未来的研究中还需要进一步了解地震耦合的时间变化，但我们的结果表明，小安的列斯群岛的俯冲带没有耦合，这挑战了1839年和1843年地震是逆冲事件的观点。现在，这项工作更新的GPS速度还揭示了少量但可检测到的弧扩展，这与弧内活动正断层的地质观测结果一致。