Cocos intraslab earthquakes were used to make shear-wave splitting measurements to explore the factors that control seismic anisotropy and to study the mantle wedge flow patterns in southeastern Mexico, where the Cocos plate subducts beneath the North American plate. Cocos intraslab earthquakes reach depths of 250 km, making it possible to sample the mantle wedge. The Silver and Chan (1991) covariance method was used to measure the splitting parameters: the fast polarization direction (φ) and the delay time (δt). The measurements can be divided into three regions: (1) northwest and (2) southeast of the Tehuantepec Ridge extension (i.e., the subducted Tehuantepec Ridge within the Cocos slab) and (3) the region above the subhorizontal Cocos slab. (1) In the first region, northeast of the 100 km isodepth contour of the Cocos slab, the fast axes are trench-perpendicular. This can be explained assuming the development of A-type olivine fabric and the existence of 2-D corner flow driven by the downdip motion of the Cocos slab. Southwest of the 100 km isodepth contour, measurements show trench-parallel fast polarization directions that are also consistent with corner flow, albeit in a serpentinized mantle wedge. Right above the Tehuantepec Ridge extension (northeast of the 100 km isodepth contour of the subducting slab), a change in the fast polarization directions from trench-normal to trench-parallel while going from northwest to southeast is observed and signals a change in the mantle flow pattern possibly through a vertical tear in the Cocos slab. 3-D toroidal flow could drive subslab mantle material around this slab edge and into the mantle wedge. (2) In the second region, the measured fast polarization directions show a trench-parallel orientation that is interpreted to result from southeastward trench-parallel flow through a serpentinized mantle wedge tip and also through a mantle wedge core made up of A- or C-type olivine fabrics with their fast axes oriented parallel to the flow direction. Trench-perpendicular fast polarization directions are observed beneath the fore-arc region of the Central America Volcanic Arc, near Tacaná Volcano, and trench-parallel polarizations are observed beneath the arc. These orientations could be explained by assuming the presence of B-type olivine fabric in the mantle wedge tip, A- or C-type olivine fabric in the mantle wedge core, and trench-parallel flow, so that the orientations of the fast axes become perpendicular to the mantle flow direction beneath the fore-arc and parallel to it beneath the arc. Lastly, (3) in the third region, over the flat slab, the observed delay times (0.04–0.42 s) are consistent with crustal anisotropy magnitudes, and the fast polarization directions seem to be controlled by the orientations of fault systems and alignments in foliations. Therefore, crustal faults and folds seem to be the dominant factors controlling the observed anisotropy.

Cocos 板内地震用于进行剪切波分裂测量，以探索控制地震各向异性的因素并研究墨西哥东南部的地幔楔流动模式，那里的Cocos 板块俯冲到北美板块下方. Cocos 板内地震达到 250 公里的深度，使得对地幔楔进行采样成为可能。Silver 和 Chan (1991) 协方差法用于测量分裂参数：快极化方向 (φ) 和延迟时间 (δt)。测量可分为三个区域：(1) Tehuantepec Ridge 延伸部（即科科斯板片内俯冲的特万特佩克洋脊）的西北和(2) 东南部和(3) 亚水平科科斯板片上方的区域。(1) Cocos板片100 km等深等深线东北方向的第一区，快轴与海沟垂直。这可以通过假设 A 型橄榄石织物的发展和 Cocos 板的下倾运动驱动的二维角流的存在来解释。100 公里等深等深线的西南，测量结果显示平行沟槽的快速极化方向也与角流一致，尽管是在蛇纹石化的地幔楔中。在 Tehuantepec 洋脊延伸部正上方（俯冲板片 100 km 等深等深线的东北方），观察到从西北到东南方向的快速极化方向从海沟法线到海沟平行的变化，这表明地幔发生了变化流动模式可能通过 Cocos 板中的垂直撕裂。3-D 环形流可以驱使板片边缘物质围绕该板片边缘进入地幔楔。(2) 在第二个区域，测得的快极化方向显示了平行沟槽方向，这被解释为是由向东南方向的沟槽平行流通过蛇纹状地幔楔尖端以及通过由具有快轴的 A 型或 C 型橄榄石织物组成的地幔楔核心产生的方向平行于流动方向。在塔卡纳附近的中美洲火山弧的弧前区域下方观察到垂直于海沟的快速极化方向在弧下观察到火山和沟槽平行极化。这些方向可以通过假设地幔楔尖端存在 B 型橄榄石织物、地幔楔核中存在 A 或 C 型橄榄石织物以及沟槽平行流动来解释，因此快轴的方向变为前弧下垂直于地幔流动方向，弧下平行于地幔流动方向。最后，（3）在第三区域，在平板上，观察到的延迟时间（0.04-0.42 s）与地壳各向异性幅度一致，快速极化方向似乎受断层系统的方向和排列控制叶面。因此，地壳断层和褶皱似乎是控制观察到的各向异性的主要因素。