Abstract We propose a new methodology for carrying out eikonal-based traveltime tomography arising from important applications such as seismic imaging and medical imaging. The new method formulates the traveltime tomography problem as a variational problem for a certain cost functional explicitly with respect to both traveltime and sound speed. Furthermore, the cost functional is penalized to e...

The first-arrival quasi-P wave traveltime field in an anisotropic elastic solid solves a first-order nonlinear partial differential equation, the q P eikonal equation. The difficulty in solving this eikonal equation by a finitedifference method is that for anisotropic media the ray (group) velocity direction is not the same as the direction of the traveltime gradient, so that the traveltime gra...

In the high frequency regime, the geometrical-optics approximation for the Helmholtz equation with a point source results in an eikonal equation for traveltime and a transport equation for amplitude. Because the point-source traveltime field has an upwind singularity at the source point, all formally high-order finite-difference eikonal solvers exhibit first-order convergence and relatively lar...

S U M M A R Y We propose a level-set adjoint-state method for crosswell traveltime tomography using both first-arrival transmission and reflection traveltime data. Since our entire formulation is based on solving eikonal and advection equations on finite-difference meshes, our traveltime tomography strategy is carried out without computing rays explicitly. We incorporate reflection traveltime d...

We derive an approximate equation combining the quality factor Q, the traveltime of a wave, and the variation of the instantaneous frequency (IF) at the envelope peaks of two successive seismic wavelets, along the wave propagating direction, based on the theory of one-way wave propagation in a 1D viscoelastic medium. We then propose a method (called the WEPIF method) to estimate Q by measuring ...

[1] In 2005 an extensive new seismic refraction data set was acquired over the central part of the Chicxulub impact crater, allowing us to image its structure with much better resolution than before. However, models derived from traveltime data are limited by the available ray coverage and the nonuniqueness that is inherent to all geophysical methods. Therefore, many different models can fit th...

Image-domain wavefield tomography is a technique that reconstructs the velocity model by extracting information from migrated images. In time-lag extended images, velocity model accuracy can be evaluated by reflection focusing error, which represents the traveltime residual in the image domain. The model is updated by minimizing an objective function similar to the one used by wave-equation tra...

S U M M A R Y We demonstrate a method for the empirical construction of 2-D surface wave phase traveltime finite frequency sensitivity kernels by using phase traveltime measurements obtained across a large dense seismic array. The method exploits the virtual source and reciprocity properties of the ambient noise cross-correlation method. The adjoint method is used to construct the sensitivity k...

Seismic migration requires an accurate background velocity model that correctly predicts the kinematics of wave propagation in the true subsurface. Least-squares migration, which seeks the inverse rather than the adjoint of a forward modeling operator, is especially sensitive to errors in this background model, which can result in traveltime differences between predicted and observed data that ...

Accurate and efficient traveltime and raypath calculation is essential for successful application of a number of important near-surface imaging techniques. To this end, we have developed a grid raytracing method that incorporates two important developments in recent traveltime modeling research, namely, fast wavefront tracking and wavefront construction. By incorporating a fast wavefront tracki...