Open AccessIrregular grids in seismic tomography and minimum‐time ray tracing
Author(s) -
Vesnaver Aldo L.
Publication year - 1996
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1996.tb05274.x
Subject(s) - ray tracing (physics) , inversion (geology) , grid , discretization , tomography , seismic tomography , tomographic reconstruction , algorithm , uniqueness , distributed ray tracing , singular value decomposition , geometry , computer science , mathematics , mathematical analysis , geology , optics , seismology , physics , tectonics
SUMMARY Tomographic inversion of traveltimes is often carried out by discretizing the Earth as a grid of regular pixels. This choice simplifies the related ray‐tracing algorithms, but contributes significantly to the non‐uniqueness of the estimated velocity distribution. A singular value decomposition of the tomographic matrix enables one to recognize the causes of this mathematical ambiguity in the model space. This is more intuitive than introducing arbitrary damping factors and spatial filters, and allows one to control the non‐uniqueness of solutions by modifying the pixel distribution or the acquisition geometry. This approach lends itself to the adoption of irregular grids and to the definition of a new ray‐tracing algorithm, based on Fermat's principle of minimum time, which is able to simulate transmitted, reflected, refracted and diffracted waves. The joint tomographic inversion of these different types of waves potentially provides an additional improvement to the quality and reliability of the estimated velocities.