Finite-Frequency Tomography of the Earth's Mantle

第一断层图像的P波变化在地球的下地幔有限频率理论（相对于经典射线理论）显示出显着增强的重要功能在深度，特别是那些较小的规模，容易受到波前愈合的影响，被忽略在经典射线理论反演方法。 特别是，压缩速度异常表明，有限数量的地幔柱（夏威夷、塔希提岛、复活节岛、佛得角）显然起源于下地幔深处，有些显然不是（冰岛、阿法尔），而其他的则还没有定论。研究人员将继续努力使用这些新的和创新的方法来改善断层图像。这将包括将短周期P波添加到目前的长周期数据集，将工作扩展到S波，并继续最近开始的计划，以系统地测量P波和S波的到达时间和振幅。研究人员还将有限频率理论扩展到复杂的3D模型，以便它可以用于较浅的调查，如USAray。他们计划扩展辐射传输理论，使其能够预测来自层析成像模型的散射能量，并预测可用于约束此类模型的可观测量。这将从振幅反转开始。最后，他们建议调查有限频率的影响，在波形反演澳大利亚上地幔使用谱元素的方法，在努力解决各种模型的异质性和各向异性之间的差异，初步结果似乎已经解决了深地幔柱的存在的主要争议。研究人员希望对下地幔中压缩性和剪切模量变化之间令人困惑的负相关性、下地幔分层的存在以及地幔柱的起源提供新的认识。此外，一些学生和博士后将接受教育，使用新的断层摄影方法。

The first tomographic images of P wave variations in the Earth's lower mantle obtained with finite-frequency theory (as opposed to classical ray theory) show a significant enhancement of important features at depth, especially those of smaller scale that are susceptible to effects of wavefront healing, that are neglected in the classical ray theoretical inversion methods. In particular, the compressional velocity anomalies show that a limited number of plumes (Hawaii, Tahiti, Easter Island, Cape Verde) clearly originate deep in the lower mantle, some clearly do not (Iceland, Afar), while the jury is still out on others. The investigators will continue efforts to improve tomographic images using these new and innovative methods. This will include adding short period P waves to the present long period data set, extending efforts to S waves, and continuing a recently begun program to measure systematically the arrival times and amplitudes of P and S waves for a range of frequencies. The investigators will also extend finite-frequency theory to complicated 3D models so it can be used for shallower investigations such as USArray. They plan to extend Radiative Transfer theory such that it can predict scattering energy from tomographic models, and predict observables that can be used to constrain such models. This will be initiated with the inversion of amplitudes. Finally, they propose to investigate finite frequency effects in waveform inversions for the Australian upper mantle using a spectral element approach, in an effort to resolve discrepancies between various models of heterogeneity and anisotropy.Preliminary results seem already to have resolved the major controversy about the existence of deep mantle plumes. The investigators expect to throw new light on the puzzling negative correlation between compressibility and shear modulus variations in the lower mantle, on the existence of a lower mantle layering, and on the origin of mantle plumes. In addition, several students and postdocs will be educated to use the new tomographic methods.