3-D simultaneous inversion for velocity and reflector geometry using multiple classes of arrivals in a spherical coordinate frame

• Published in: Journal of seismology 2014, Vol.18 (1), p.123-135
• Main Authors: Huang, Guo-jiao, Bai, Chao-ying, Li, Xing-wang, Greenhalgh, Stewart
• Format: Article
• Language: English
• Subjects: 3-D technology; Algorithms; Arrivals; Discontinuity; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Earthquakes, seismology; Engineering and environment geology. Geothermics; Exact sciences and technology; Geophysics; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Internal geophysics; Inversions; Mathematical models; Natural hazards: prediction, damages, etc; Noise levels; Original Article; Ray tracing; Reflectors; Seismology; Structural Geology; Studies; Three dimensional; Travel time; Velocity
• ISSN: 1383-4649; 1573-157X
• DOI: 10.1007/s10950-013-9406-z

The two key requirements in conducting 3-D simultaneous traveltime tomography on real data at the regional and global scale with multiple classes of arrival time information are (1) it needs an efficient and accurate arrival tracking algorithm for multiply transmitted, reflected (or refracted) and converted waves in a 3-D variable velocity model with embedded velocity discontinuities (or subsurface interfaces), and (2) a subdimensional inversion solver is required which can easily search for different types of model parameters to balance the trade-off between the different types of model parameter updated in the simultaneous inversion process. For these purposes, we first extend a popular grid/cell-based wavefront expanding ray tracing algorithm (the multistage irregular shortest-path ray tracing method), which previously worked only in Cartesian coordinate at the local scale, to spherical coordinates appropriate to the regional or global scale. We then incorporated a fashionable inversion solver (the subspace method) to formulate a simultaneous inversion algorithm, in which the multiple classes of arrivals (including direct and reflected arrivals from different velocity discontinuities) can be used to simultaneously update both the velocity fields and the reflector geometries. Numerical tests indicate that the new inversion method is both applicable and flexible in terms of computational efficiency and solution accuracy, and is not sensitive to a modest level of noise in the traveltime data. It offers several potential benefits over existing schemes for real data seismic imaging.