We overview a wide range of traveltime computation methods, most of them novelties from the last five years or so. We first classify the methods, then we give a standardized description. This unified form allows a convenient comparison of these methods. Each description first outlines the basics principles of the given method. It then identifies its main features: assumptions made on the veloci...

S U M M A R Y In this paper, several methods for the solution of the eikonal equation are investigated. Using the method of characteristics, traveltimes are computed along rays. Approximate solutions of the eikonal equation can also be obtained. From Fermat’s principle, first-order changes in the traveltime can be found by integrating along initial ray trajectories. Alternatively, linearized ra...

[1] The thermal and compositional structure of oceanic lithosphere, which exerts an important control on plate behavior, is still debated. Our set of 60,000 PP-P and SS-S traveltime differences with oceanic PP and SS bounce points provides a good constraint on both compressionaland shear-wave velocity. By calculating traveltimes for thermal models that are converted to seismic structures with a...

SUMMARY Traveltime data together with known spacing between sources and receivers for seismic transmission tomography can be used to determine rigorous constraints on the minimum and maximum wave speeds in the propagating medium. These constraints lead to a new minimum variance criterion on inversion algorithms. These results do not improve the velocity reconstructions directly , but provide ri...

Wavefront healing, in which diffractions interfere with directly traveling waves causing a reduction in recorded traveltime delays, has been postulated to cause a bias towards faster estimated Earth models. This paper reviews the theory from the mathematical physics community that explains the properties of diffractions and applies it to a suite of increasingly complicated numerical examples. W...

The purpose of this research was to test the proposition that the mantle beneath New York and Southern New England is divided into several "anisotropic domains" that are the seismic expression of the plate tectonic process of "terrain accretion". Were such the case, we would expect different directions of the shear wave fast direction and different mean shear wave velocities in each of the seve...