Rift-Rift-Rift triple junctions are regions where three plates interact, generating complex networks of variably oriented faults. While the geometry of the fault networks is easily constrained from their surface expression, what remains unclear is how the kinematics of faults and their interactions vary spatially, and how these relate to the unusual crustal motions that result from three plates diverging from each other. The Afar depression lies at the triple junction between the African, Arabian, and Somalian plates (in the Horn of Africa), where the unique combination of observational data from structural mapping, seismicity, and Global Navigation Satellite System (GNSS) allows us to understand the link between fault kinematics and plate motions. We complement these observations with an analog model to gain insights into how the patterns and directions of faults relate to overall plate motions. A key finding in both the model and nature is that some adjacent normal faults form at high angles and generate T-shaped structures. These purely normal faults are synchronously active, which means that the extension direction varies ~90° locally. These kinematic contrasts in our model and in nature occur despite the relatively smooth pattern of overall surface motions. The results indicate that normal faults interacting at high angles to form the T-shaped structures can evolve synchronously within a stress field that varies gently in magnitude but dramatically in orientation over a few kilometers.

中文翻译：

---

协调裂谷-裂谷-裂谷三重连接处的板块运动和断层作用

裂谷-裂谷-裂谷三重交界处是三个板块相互作用的区域，形成由不同方向的断层组成的复杂网络。虽然断层网络的几何形状很容易受到其表面表达的限制，但目前尚不清楚的是断层的运动学及其相互作用如何在空间上变化，以及它们与三个板块相互偏离所导致的不寻常的地壳运动有何关系。阿法尔凹陷位于非洲、阿拉伯和索马里板块（非洲之角）之间的三重交界处，来自结构测绘、地震活动和全球导航卫星系统 (GNSS) 的观测数据的独特组合使我们能够了解断层运动学和板块运动之间的联系。我们用模拟模型补充这些观察结果，以深入了解断层的模式和方向与整体板块运动的关系。模型和自然界的一个重要发现是，一些相邻的正断层以高角度形成并生成 T 形结构。这些纯正断层是同步活动的，这意味着延伸方向局部变化~90°。尽管整体表面运动的模式相对平滑，但我们的模型和自然界中的这些运动学对比仍然存在。结果表明，正断层以大角度相互作用形成T形结构可以在应力场内同步演化，该应力场的大小变化平缓，但方向在几公里范围内变化剧烈。