The Alpine chain in western and central Europe is a complex orogen developed as a result of the African–Adriatic plate convergence towards the European continent and the closure of several Tethys oceanic branches. Seismic tomography studies detected high-wave-speed slabs plunging beneath the orogen to variable depths and a potential change in subduction polarity beneath the Central Alps. Alpine subduction is expected to leave a significant imprint on the surrounding mantle fabrics, although deformation associated with the Hercynian Orogeny, which affected Europe prior to the collision with Adria, may have also been preserved in the European lithosphere. Here we estimate SKS anisotropy beneath the central and greater Alpine region at 113 broadband seismic stations from the AlpArray experiment as well as permanent networks from Italy, Switzerland, Austria, Germany, and France. We compare the new improved dataset with previous studies of anisotropy, mantle tomography, lithospheric thickness, and absolute plate motion, and we carry out Fresnel analysis to place constraints on the depth and origin of anisotropy. Most SKS directions parallel the orogen strike and the orientation of the Alpine slabs, rotating clockwise from west to east along the chain, from −45 to 90^∘ over a ∼700 km distance. No significant changes are recorded in Central Alps at the location of the putative switch in subduction polarity, although a change in direction variability suggests simple asthenospheric flow or coupled deformation in the Swiss Central Alps transitions into more complex structures beneath the Eastern Alps. SKS fast axes follow the trend of high seismic anomalies across the Alpine Front, far from the present-day boundary, suggesting slabs act as flow barriers to the ambient mantle surrounding them for hundreds of km. Further north across the foreland, SKS fast axes parallel Hercynian geological structures and are orthogonal to the Rhine Graben and crustal extension. However, large splitting delay times (>1.4 s) are incompatible with a purely lithospheric contribution but rather represent asthenospheric flow not related to past deformational events. West of the Rhine Graben, in northeastern France, anisotropy directions are spatially variable in the proximity of a strong positive seismic anomaly in the upper mantle, perhaps perturbing the flow field guided by the nearby Alpine slabs.

中文翻译：

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地幔流在中部和更大的高山区域以下：AlpArray和永久性站点的SKS各向异性分析的见解

西非和中欧的高山链是由于非洲亚得里亚海板块向欧洲大陆汇合以及几个特提斯海洋分支的封闭而形成的复杂造山带。地震层析成像研究发现，高速平板从造山带下方跌落至可变深度，并且俯冲极性在中部阿尔卑斯山下方可能发生变化。尽管在欧洲岩石圈中也可能保留了与海西造山带有关的变形，该变形在与阿德里亚碰撞之前影响了欧洲，但高山俯冲作用将在周围的地幔结构上留下重要的印记。在这里，我们根据AlpArray实验以及意大利，瑞士，奥地利，德国和法国。我们将新的改进数据集与以前对各向异性，地幔层析成像，岩石圈厚度和绝对板块运动的研究进行了比较，并且我们进行了菲涅耳分析，以对各向异性的深度和起源进行约束。大多数SKS方向与造山带走向和高山板块的方向平行，沿着链条从西向东顺时针旋转，从â???? 45至90 ^â???? 超过¼700千米的距离。尽管俯冲极性的变化表明在瑞士阿尔卑斯山中简单的软流圈流动或耦合变形转变为东阿尔卑斯山以下更复杂的结构，但在俯冲极性的假定开关位置的阿尔卑斯山中没有记录到明显变化。SKS快轴遵循远离当前边界的整个阿尔卑斯锋面高地震异常的趋势，这表明平板对周围数百公里的地幔起着流动屏障的作用。在前陆的更北端，SKS快轴平行于海西地质结构，并与莱茵河格拉本和地壳扩展正交。但是，较大的分割延迟时间（> 1.4？s）与纯岩石圈的贡献不兼容，而是代表与过去的变形事件无关的软流圈流量。在法国东北部的莱茵格拉本以西，各向异性的方向在上地幔强烈的正地震异常附近是空间可变的，这可能会扰动附近高山平板引导的流场。