The South Chile ridge (SCR) intersects the Patagonian trench around 46°09′S, forming the triple junction among the Antarctic, Nazca, and South America plates. Subduction of the SCR since ~18 Ma produced the opening of a slab window beneath Patagonia and a noticeable magmatic gap in the cordillera, profuse volcanism and topographic uplift in the retroarc. To study seismicity distribution and present-day stress resulting from this particular framework, we analyse databases of seismic events and earthquake focal mechanisms. Our study finds that clusters of intraplate crustal seismic events are disrupted by a ~450–470 km seismicity gap above the slab window. Calculated stress tensors depict a strike-slip tectonic regime north of the triple junction, and ~W-E compression to the south of the seismic gap. We propose that the seismotectonic behaviour of the upper plate is disturbed at the first order by the trench-ridge intersection, leading to a heterogeneous stress field.

中文翻译：

---

巴塔哥尼亚安第斯山脉下智利南脊俯冲的地震构造意义

南智利海脊 (SCR) 在 46°09'S 附近与巴塔哥尼亚海沟相交，形成南极、纳斯卡和南美洲板块之间的三重连接。大约 18 Ma 以来 SCR 的俯冲在巴塔哥尼亚下方产生了一个板状窗口，并且在山脉中出现了明显的岩浆间隙，在弧后有大量的火山活动和地形隆起。为了研究由这个特定框架产生的地震活动分布和当前应力，我们分析了地震事件和地震震源机制的数据库。我们的研究发现，板内地壳地震事件的集群被板窗上方约 450-470 公里的地震活动间隙破坏。计算出的应力张量描绘了三重交界以北的走滑构造体系，以及地震间隙以南的~WE压缩​​。