Big ray-tracing and eikonal solver on unstructured grids: Application to the computation of a multivalued traveltime field in the Marmousi model

This paper presents a numerical computation of the multivalued traveltime field generated by a point-source experiment in the Marmousi model. Two methods are combined to achieve this goal: a method called big ray tracing, used to compute multivalued traveltime fields, and an eikonal solver, designed to work on unstructured meshes. Big ray tracing is based on a combination of ray tracing and local solutions of the eikonal equation. Classical ray tracing first discretizes the phase space and defines local zones that possibly overlap where the traveltime field is multivalued. Then an eikonal solver computes traveltimes in these zones called big rays. It acts as an exact interpolation process between rays associated with different branches of the traveltime field. The geometry of big rays may be complicated and is better discretized using unstructured meshes. An eikonal solver designed to work on unstructured meshes is used.