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Titolo:
Multiscale seismic tomography
Autore:
Chiao, LY; Kuo, BY;
Indirizzi:
Natl Taiwan Univ, Inst Oceanog, Taipei 10764, Taiwan Natl Taiwan Univ Taipei Taiwan 10764 Inst Oceanog, Taipei 10764, Taiwan Acad Sinica, Inst Earth Sci, Taipei 115, Taiwan Acad Sinica Taipei Taiwan 115 Sinica, Inst Earth Sci, Taipei 115, Taiwan
Titolo Testata:
GEOPHYSICAL JOURNAL INTERNATIONAL
fascicolo: 2, volume: 145, anno: 2001,
pagine: 517 - 527
SICI:
0956-540X(200105)145:2<517:MST>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
CORE-MANTLE BOUNDARY; DIFFERENTIAL TRAVEL-TIMES; VELOCITY STRUCTURE; HIGH-RESOLUTION; INVERSION; MODEL; UNCERTAINTY; ARTIFACTS; WAVELETS; KERNELS;
Keywords:
D '' layer; inverse theory; tomography;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
46
Recensione:
Indirizzi per estratti:
Indirizzo: Chiao, LY Natl Taiwan Univ, Inst Oceanog, Taipei 10764, Taiwan Natl TaiwanUniv Taipei Taiwan 10764 nog, Taipei 10764, Taiwan
Citazione:
L.Y. Chiao e B.Y. Kuo, "Multiscale seismic tomography", GEOPHYS J I, 145(2), 2001, pp. 517-527

Abstract

Seismic traveltime tomography is commonly discretized by a truncated expansion of the pursued model in terms of chosen basis functions. Whether parametrization affects the actual resolving power of a given data set as well as the robustness of the resulting earth model has long been seriously debated. From the perspective of the model resolution, however, there is one important aspect of the parametrization issue of seismic tomography that has yet to be systematically explored, that is, the space-frequency localizationof a chosen parametrization. In fact, the two most common parametrizationstend to enforce resolution in each of their own particular domains. Namely, parametrization in terms of spherical harmonics with global support tendsto emphasize spectral resolution while sacrificing the spatial resolution,whereas the compactly supported pixels tend to behave in the opposite manner. Some of the significant discrepancies among tomographic models are verylikely to be manifestations of this effect, when dealing with data sets with nonuniform sampling. With an example of the tomographic inversion for the lateral shear wave heterogeneity of the D " layer using S-SKS traveltimes, we demonstrate an alternative parametrization in terms of the multiresolution representation of the pursued model function. Unlike previous attemptsof multiscale inversion that invoke pixels with variable sizes, or overlayseveral layers of tessellation with different grid intervals, our formulation invokes biorthogonal generalized Harr wavelets on a sphere. We show that multiresolution representation can be constructed very easily from an existing block-based discretization. A natural scale hierarchy of the pursued model structure constrained by the resolving power of the given sampling isembedded within the solution obtained. It provides a natural regularization scheme based on the actual ray-path sampling and is thus free from a priori prejudices intrinsic to most regularization schemes. Unlike solutions obtained through spherical harmonics or spherical blocks that tend to collapse structures onto ray paths, our parametrization imposes regionally varyingNyquist limits, that is, robustly resolvable local wavelength bands withinthe obtained solution.

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Documento generato il 18/01/20 alle ore 21:39:57