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Full-wave seismic sensitivity in a s...

Nissen-Meyer, Tarje Florian.

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Full-wave seismic sensitivity in a spherical earth.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Full-wave seismic sensitivity in a spherical earth./
作者:	Nissen-Meyer, Tarje Florian.
面頁冊數:	196 p.
附註:	Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6553.
Contained By:	Dissertation Abstracts International68-10B.
標題:	Geophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3286128
ISBN:	9780549284918

Full-wave seismic sensitivity in a spherical earth.
Nissen-Meyer, Tarje Florian.

Full-wave seismic sensitivity in a spherical earth. - 196 p.

Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6553.

Thesis (Ph.D.)--Princeton University, 2007.

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.

ISBN: 9780549284918Subjects--Topical Terms:

535228
Geophysics.

Full-wave seismic sensitivity in a spherical earth.
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