Full-wave seismic sensitivity in a spherical earth
- 出版日期：2007.
- 页数：1 online resource.
- 第一责任说明：Tarje Florian Nissen-Meyer.
- 分类号：a631
- ISBN：9780549284918(e-book) :
MARC全文
62h0047124 20131202140549.0 cr an |||||||| 131023s2007 a fsbm |000|0 eng | 3286128 9780549284918(e-book) : CNY371.35 NGL eng NGL a631 Nissen-Meyer, Tarje Florian. Full-wave seismic sensitivity in a spherical earth [electronic resource] / Tarje Florian Nissen-Meyer. 2007. 1 online resource. Description based on online resource; title from title page (viewed Oct. 23, 2013) Thesis (Ph.D.)--Princeton University, 2007. Includes bibliographical references. This dissertation revolves around aspects of both the seismic forward and inverse problem, blending a new 2-D spectral-element method to account for wave effects with a finite-frequency approach to global seismic tomography. The overall objective is to perform inversions at arbitrary seismic frequencies based on any portion of a seismogram, including phases such as those caused by diffraction, triplications, or caustics. Motivated by the sparsely sampled but highly heterogeneous and geodynamically critical lowermost mantle, we strive to exploit core-grazing waves such as Pdiff which shall drastically improve coverage and resolution of 3-D velocity images, provided one has access to high-frequency (e.g. 1Hz) data. To remediate previous resolution shortcomings via such wave phenomena, one needs to calculate exact Frechet sensitivity kernels based on the full-wave equation. Unfortunately, computational limitations deter from using 3-D wave propagation. Instead, we exploit the symmetry of seismic-wave radiation patterns in spherically symmetric reference models, thereby collapsing 3-D elastodynamics to a series of six equivalent 2-D problems while accounting for the full 3-D complexity of sensitivity kernels. The core of this work is a 2-D spectral-element method that solves such a system to compute the relevant wavefields that constitute sensitivity kernels. Upon deriving the system of equations and the spectral-element discretization thereof, various examples underpin the accuracy and efficiency of all relevant aspects of the method: Using well-established and newly developed analytical reference solutions and illustrative wavefield snapshots, we validate moment-tensor and axial discretization, optimal mesh generation, parallelization and domain decomposition, solid-fluid configuration, energy conservation, global wave propagation, and a new time integration scheme. We then show how to extract full-waveform, traveltime and amplitude sensitivity kernels for any part of a seismogram, before exploring some of their dependencies such as source frequency and depth, excitation type, phase type, and epicentral distance. This establishes an a priori view into how, when, and where seismograms are sensitive to 3-D earth signature. A once-and-for-all wavefield database for various source depths will then serve as a complete set of global time-space sensitivity for a given background model, thereby allowing for tomographic inversions with arbitrary frequencies, observables, and phases. Seismic prospecting. Electronic dissertations local. aInternet resource. aCN b010001 http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=2ptpMxV6U%2fY%3d 010001 Bs2740 rCNY371.35 ; h1 bs1312