Topographic corrections to slowness measurements in parsimonious migration of land data

Parsimonious migration requires that incident and emergent angles be measured, via apparent slownesses, from the seismic data being migrated. When slownesses are measured from land data, it is the apparent slowness along the topography, not the horizontal slowness that is being measured. Thus, errors are introduced into the incident and emergent angle estimates, which are defined via horizontal slownesses. These errors can be corrected using the local topographic dips. A 2D field data example shows that, after correction, a migrated image has significantly improved coherency.