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A mixed unsplit-field PML-based sche...

Kang, Jun Won.

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A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves./
作者:	Kang, Jun Won.
面頁冊數:	269 p.
附註:	Source: Dissertation Abstracts International, Volume: 71-09, Section: B, page: 5652.
Contained By:	Dissertation Abstracts International71-09B.
標題:	Applied Mechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3417465
ISBN:	9781124173535

A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves.
Kang, Jun Won.

A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves. - 269 p.

Source: Dissertation Abstracts International, Volume: 71-09, Section: B, page: 5652.

Thesis (Ph.D.)--The University of Texas at Austin, 2010.

We discuss a full-waveform based material profile reconstruction in two-dimensional heterogeneous semi-infinite domains. In particular, we try to image the spatial variation of shear moduli/wave velocities, directly in the time-domain, from scant surficial measurements of the domain's response to prescribed dynamic excitation. In addition, in one-dimensional media, we try to image the spatial variability of elastic and attenuation properties simultaneously.

ISBN: 9781124173535Subjects--Topical Terms:

1018410
Applied Mechanics.

A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves.
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245 1 2 $a A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves.
300 $a 269 p.
500 $a Source: Dissertation Abstracts International, Volume: 71-09, Section: B, page: 5652.
500 $a Adviser: Loukas F. Kallivokas.
502 $a Thesis (Ph.D.)--The University of Texas at Austin, 2010.
520 $a We discuss a full-waveform based material profile reconstruction in two-dimensional heterogeneous semi-infinite domains. In particular, we try to image the spatial variation of shear moduli/wave velocities, directly in the time-domain, from scant surficial measurements of the domain's response to prescribed dynamic excitation. In addition, in one-dimensional media, we try to image the spatial variability of elastic and attenuation properties simultaneously.
520 $a To deal with the semi-infinite extent of the physical domains, we introduce truncation boundaries, and adopt perfectly-matched-layers (PMLs) as the boundary wave absorbers. Within this framework we develop a new mixed displacement-stress (or stress memory) finite element formulation based on unsplit-field PMLs for transient scalar wave simulations in heterogeneous semi-infinite domains. We use, as is typically done, complex-coordinate stretching transformations in the frequency-domain, and recover the governing PDEs in the time-domain through the inverse Fourier transform. Upon spatial discretization, the resulting equations lead to a mixed semi-discrete form, where both displacements and stresses (or stress histories/memories) are treated as independent unknowns. We propose approximant pairs, which numerically, are shown to be stable.
520 $a The resulting mixed finite element scheme is relatively simple and straightforward to implement, when compared against split-field PML techniques. It also bypasses the need for complicated time integration schemes that arise when recent displacement-based formulations are used. We report numerical results for 1D and 2D scalar wave propagation in semi-infinite domains truncated by PMLs. We also conduct parametric studies and report on the effect the various PML parameter choices have on the simulation error.
520 $a To tackle the inversion, we adopt a PDE-constrained optimization approach, that formally leads to a classic KKT (Karush-Kuhn-Tucker) system comprising an initial-value state, a final-value adjoint, and a time-invariant control problem. We iteratively update the velocity profile by solving the KKT system via a reduced space approach. To narrow the feasibility space and alleviate the inherent solution multiplicity of the inverse problem, Tikhonov and Total Variation (TV) regularization schemes are used, endowed with a regularization factor continuation algorithm. We use a source frequency continuation scheme to make successive iterates remain within the basin of attraction of the global minimum. We also limit the total observation time to optimally account for the domain's heterogeneity during inversion iterations.
520 $a We report on both one- and two-dimensional examples, including the Marmousi benchmark problem, that lead efficiently to the reconstruction of heterogeneous profiles involving both horizontal and inclined layers, as well as of inclusions within layered systems.
590 $a School code: 0227.
650 4 $a Applied Mechanics. $3 1018410
650 4 $a Geophysics. $3 535228
650 4 $a Engineering, Civil. $3 783781
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690 $a 0373
690 $a 0543
710 2 $a The University of Texas at Austin. $3 718984
773 0 $t Dissertation Abstracts International $g 71-09B.
790 1 0 $a Kallivokas, Loukas F., $e advisor
790 $a 0227
791 $a Ph.D.
792 $a 2010
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3417465