Travel time tomography with adaptive dictionaries

TitleTravel time tomography with adaptive dictionaries
Publication TypeJournal Article
Year of Publication2018
AuthorsBianco M.J, Gerstoft P
Date Published2018/12
Type of ArticleArticle
ISBN Number2333-9403
Accession NumberWOS:000450358500001
Keywordsalgorithm; deconvolution; Dictionary learning; Engineering; geophysics; Imaging Science & Photographic Technology; inverse problems; l1; Machine learning; norm; overcomplete dictionaries; regularization; seismic tomography; Seismology; sparse; sparse modeling; speed; wave-form inversion

We develop a two-dimensional travel time tomography method, which regularizes the inversion by modeling groups of slowness pixels from discrete slowness maps, called patches, as sparse linear combinations of atoms from a dictionary. We propose to use dictionary learning during the inversion to adapt dictionaries to specific slowness maps. This patch regularization, called the local model, is integrated into the overall slowness map, called the global model. The local model considers small-scale variations using a sparsity constraint, and the global model considers larger-scale features constrained using l(2) regularization. This strategy in a locally sparse travel time tomography (LST) approach enables simultaneous modeling of smooth and discontinuous slowness features. This is in contrast to conventional tomography methods, which constrain models to be exclusively smooth or discontinuous. We develop a maximum a posteriori formulation for LST and exploit the sparsity of slowness patches using dictionary learning. The LST approach compares favorably with smoothness and total variation regularization methods on densely, but irregularly sampled synthetic slowness maps.

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