Combination of Geomechanical Modelling and Tomography to Resolve Severe Velocity Variations Below Rugose Seafloor

Seismic imaging and depth-velocity modelling below a seafloor with complex topography are always challenging. The problems are caused by two types of lateral velocity variations: (1) contrast between the water and sediments and (2) velocity variations within shallow sediments created by the variable water depth. Geomechanical effects contribute to velocity variations in shallow sediments. Variable water depth always creates some variations in overburden pressure and variable pressure changes seismic velocities. We propose a new version of tomographic inversion that is focused (constrained) to recover these types of geomechanical (compaction driven) velocity anomalies associated with rugose seafloor. Applied together with geomechanical modelling and standard seismic tomography it helps to solve the strongest and most complicated water bottom related velocity anomalies. Synthetic and real data examples illustrate how this combination works.