Depth Resolution of Anisotropy using Body Waves

Schulte-Pelkhamstan-0310372本研究的目的是获得地壳和上地幔地震各向异性深度分布的新约束。地震各向异性是地幔变形的一个指标，而分离来自不同深度的信号的能力，例如来自岩石圈与软流圈的信号，使我们能够对变形随深度的分布有新的认识，从而了解板幔耦合的性质和板块构造的驱动力。有几种方法可以检测地震各向异性，如横波分裂、P波偏振异常和Pn方位角速度变化。这些阶段有不同的深度各向异性的敏感性，使所有测量的组合提供了新的约束垂直变化的各向异性。此外，横波分裂和P波偏振异常已被证明是频率依赖于垂直变化的各向异性介质，但这种效果的量化，可应用于观测尚未开发。该项目的第一部分是通过数值正演模拟和对合成数据的测量来量化不同体波方法之间的深度灵敏度差异和频率依赖行为。第二部分是将由此产生的基准应用于全球地震网的数据。就更广泛的影响而言，这些结果将为地震学家、地球动力学家和更广泛的社区提供与板块-地幔相互作用相关的新工具和见解。由此产生的分析准则可能是特别有用的数据集预期从地球镜程序。将地震各向异性与地球动力学更定量地联系起来将促进跨学科的研究。研究生参与直接相关的项目。

Schulte-PelkhamEAR-0310372The goal of this research is to derive new constraints for the depth distribution of seismic anisotropy in the crust and upper mantle. Seismic anisotropy is an indicator of deformation in the mantle, and the ability to separate signals from different depths, such as from the lithosphere versus the asthenosphere, allows new insights into the distribution of deformation with depth, and therefore into the nature of plate-mantle coupling and the driving forces of plate tectonics. There are several techniques to detect seismic anisotropy, such as measurements of shear wave splitting, P wave polarization anomalies, and Pn azimuthal velocity variations. These phases have different depth sensitivities for anisotropy, so that the combination of all measurements provides new constraints on vertically varying anisotropy. In addition, shear wave splitting and P wave polarization anomalies have shown to be frequency dependent in vertically varying anisotropic media, but a quantification of this effect that can be applied to observations has yet to be developed. The first part of this project is to quantify the differences in depth sensitivity between different body wave methods and the frequency dependent behavior, through numerical forward modeling and measurements on synthetic data. The second part is the application of the resulting benchmarks to data from the Global Seismic Network. In terms of broader impacts, these results will provide new tools and insights relevant to plate-mantle interaction to seismologists, geodynamicists, and the wider community. The resulting analysis guidelines may be especially useful for datasets anticipated from the EarthScope program. Linking seismic anisotropy more quantitatively to geodynamics will foster interdisciplinary research. Graduate students are involved in directly related projects.