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...

[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...

Spherical coordinates are a natural orthogonal system to describe wavefronts emanating from a point source. While a regular grid distribution in the Cartesian coordinate system tends to undersample the wavefront description near the source (the highest wavefront curvature) and oversample it away from the source, spherical coordinates, in general, provide a more balanced grid distribution to cha...

The present article outlines an innovative derivation of the well-known CRS traveltime formula. This is made possible by approximating the isochrones tangent to a small reflecting element embedded in a 3D homogeneous auxiliary medium. The arising paraxial traveltime formula is then parametrised by six attributes, each one characterising geometrically the wavefront of the reference normal-incide...

In this paper we present the program AMTCLAB, a MATLAB-based computer code that analyzes the traveltime distribution and performs quality analysis at the pre-inversion stage for elliptically anisotropic media explored via 2D transmission experiments. This software generalizes the program MTCLAB presented in the past for the case of layered isotropic media, and makes use of traditional and robus...