In this study new isotropic P- and S-wave velocity models as well as the P-wave azimuthally anisotropic model of the crust and uppermost mantle beneath southern Sumatra are derived from regional earthquake data by using the eikonal equation-based seismic tomography method. All the tomographic results reveal a clear high-velocity (high-V) belt in the uppermost mantle that represents the subducting Indo-Australian slab. In the mantle wedge, relatively low velocity (low-V) anomalies are clearly imaged, which may be related to the ascending fluids and partial melts caused by slab dehydration. The P-wave azimuthally anisotropic model shows complex patterns in the upper crust, which may be due to the effects of the maximum horizontal compressive stress and/or geological structure. Trench-normal fast velocity directions (FVDs) prevail in the lower crust, which may be associated with the plastic flow induced by the oblique plate convergence. Predominant trench-parallel FVDs in the fore-arc and volcanic-arc mantle wedge and trench-normal FVDs in the back-arc mantle wedge are observable, which are possibly related to 2-D slab-driven corner flow and/or 3-D complex mantle flow. The subducting slab generally displays trench-parallel FVDs, suggesting that the slab may keep the original fossil anisotropy.

在这项研究中，使用基于Eikonal方程的地震层析成像方法，从区域地震数据中得出了新的各向同性的P波和S波速度模型，以及苏门答腊南部南部地壳和最上地幔的P波方位角各向异性模型。所有断层扫描结果都显示出最上层地幔中有一条清晰的高速（高V）带，它代表了俯冲的印澳板。在地幔楔中，可以清晰地看到相对较低的速度（低V）异常，这可能与平板脱水引起的上升流体和部分熔体有关。P波方位各向异性模型在上地壳中显示出复杂的模式，这可能是由于最大水平压应力和/或地质结构的影响所致。在下地壳中普遍存在沟槽法线快速速度方向（FVDs），这可能与斜板会聚引起的塑性流动有关。可以观察到前弧和火山弧地幔楔中主要的平行于沟槽的FVD和后弧地幔楔中的垂直于沟槽的FVD，这可能与2-D平板驱动的角流和/或3-D有关复杂的地幔流。俯冲板块通常显示平行于沟槽的FVD，这表明该板块可以保持原始的化石各向异性。