3D seismic travel time surveying a comparison of the time–term method and tomography (an example from an archaeological site)

The seismic tomography is an almost exclusive method in routine interpretation of 3D refraction datasets. However, the gradient model usually used for the tomography methods might not always be the most suitable one. In some cases, the layer-based model might be more appropriate. In this article, one simple layer-based approach is introduced, based on a modification of the time–term method. It enables computation of lateral velocity changes of a refractor in highly heterogeneous media. Applications and results of these two methods are then compared on the example of a seismic survey at a medieval castle. This case study proved that the time–term approach may yield results which surpass the tomography ones. However, a combination of the two methods is recommended.