Traveltime estimation using a model‐based interpolation ray‐tracing method for layered models

Abstract

Many wavefront‐construction methods require continuous velocity models as inputs. In layered velocity models, the model is described with several isotropic or anisotropic layers, often homogeneous in each layer. Because rays will often bend sharply when crossing an interface, and can terminate because of post‐critical incidence, keeping track of the logical construction of a wavefront mesh from layer to layer is very difficult, especially with complex geometries. This is why many wavefront‐construction methods do not utilize layered models. On the other hand, many conventional ray‐tracing methods can handle layered models, but they do not have any adaptive control of ray density during wave propagation and are less efficient. Here we propose a new Model‐Based Interpolation (MBI) ray‐tracing scheme that allows a wavefront‐oriented ray algorithm to efficiently and easily incorporate layered models. The new MBI approach is essentially a wavefrontconstruction (WFC) method in that it explicitly tracks the geometry of a propagating wavefront using a mesh, which means that it can then adaptively control ray density and that it can map multivalued solutions for traveltime and amplitude on the free surface. However, instead of propagating and interpolating the wavefronts with a constant increment of traveltime as in conventional WFC, interpolation of wavefronts is performed only at layer interfaces. Modeling results for several isotropic and anisotropic layered models and a salt dome model show the potential strengths of this method as an efficient modeling tool.