Discontinuities and mantle deformation in the subduction zones of South America and Indonesia

俯冲是板块运动和地球内部动态过程的一个组成部分。到目前为止，与俯冲过程相关的变形还没有被很好地理解。地震各向异性是这些动态过程的一种可测量的物理表达，允许推断地球内部的地幔流动。以往的研究往往表明，快速极化轴的方向与俯冲板块的运动垂直，而不是像地幔橄榄石对齐所期望的那样平行。这导致了沟槽平行流动或矿物学影响的假设。各向异性的横向变化进一步表明，简单的二维模型往往不足以解释观测结果。因此，单站测量并不能可靠地反映出地球内部的过程。波茨坦的GEOFON数据档案馆可能提供印度尼西亚和南美洲俯冲带记录的大量地震学数据集。这些监测网的台数和密度大大超过了以往的研究，可以高分辨率地确定这些地区的横向剪切波分裂，从而确定这些地区的各向异性。较小的站间距允许检测小规模的横向变化，因此可以提供复杂动态过程的详细图像。为了模拟和正确解释由此产生的观测结果，必须对地震构造、层厚和不连续面有精确的了解。在第一个资助期内，开发了新的技术来改进S接收函数和SKS分裂分析的方法。已要求提供调查所需的数据，并对其进行了预处理。在安第斯中央俯冲地区，利用ReFuCA项目的资料，从SKS和附加的局部S震相研究了横波分裂。先前关于快轴的沟槽平行方向或高达3秒的大延迟时间的观察结果在这项研究中都不能得到证实。在第二个应用阶段，将利用安第斯山脉中部和南部记录的其他数据集(IPOC、ISSA)扩展和完成这项研究，以获得地震各向异性复杂性的详细图像。结果将与在印度尼西亚爪哇中部地区进行的一项研究进行比较。其目的是高分辨率地将SKS相和局部S相的各向异性图案映射到这些俯冲带中的变形过程。FD波形建模将被用来测试可能解释观测结果的不同各向异性模型的可信程度。最后，必须检查为什么新的结果与之前的观察结果不匹配。

Subduction is an integral part of plate movement and of the dynamic processes in the Earth's interior. The deformation associated with subduction processes are not well understood, so far. Seismic anisotropy is a measurable physical expression of these dynamic processes allowing to infer mantle flow in the Earth's interior. Previous studies have often shown orientation of the fast polarization axis perpendicular to the movement of the subducting plate instead of a parallel orientation as it is expected from the alignment of mantle olivine. This led to the assumption of trench-parallel flow or mineralogical influences. Lateral changes of the anisotropy further show that simple two-dimensional models are often insufficient to explain the observations. And so, measurements at single station do not reliably image the processes in the Earth's interior. The GEOFON data archive in Potsdam may provide extensive seismological data sets recorded in the subduction zones of Indonesia and South America. The station number as well as the density of these monitoring networks significantly exceed those of previous studies and allow for high-resolution determination of the lateral shear-wave splitting and thus the anisotropy in these regions. The small station spacing allows for detection of small-scale lateral changes and may thus provide a detailed image of the complex dynamic processes. In order to model and correctly interpret the resulting observations a precise knowledge of the seismic structures, layer thicknesses and discontinuities is mandatory.During the first funding period new techniques have been developed to improve the methods of S-receiver functions and SKS-splitting analysis. The data required for the investigation have been requested and pre-processed. For the area of the central Andean subduction shear wave splitting has been investigated from SKS and additional local S-phases utilizing data from the ReFuCA project. Previous observations neither of trench-parallel orientations of the fast axes nor of the large delay times of up to 3 seconds could not be confirmed in this study. During the second application period the study will be extended and completed by other data sets (IPOC, ISSA) recorded in the central and southern Andes in order to obtain a detailed image op the complexity of the seismic anisotropy. The results will be compared to a study conducted in the area of central Java, Indonesia. The aim is to map anisotropy patterns from SKS- and local S-phases with high-resolution to image deformation processes in these subduction zones. FD waveform modeling will be used to test for the plausibility of different anisotropy models that may explain the observations. Finally, it has to be examined, why the new results do not match to the previous observations.