Deformable layer tomostatics with 3D gradient velocity models

Abstract

Summary Tomostatics is a technology to quantify near-surface effects and static corrections for seismic exploration and production. Most tomostatics methods use first arrivals of seismic data to invert for a near-surface velocity model and estimate the static corrections based on the model. We present a 3D tomostatics method based on deformable layer tomography (DLT) with 3D gradient velocity models. Because the near-surface velocity fields in many areas are composed of thickness-varying velocity layers, the DLT method focus on inverting for the thicknesses of model layers and layer velocities. To account for inhomogeneous distribution of ray coverage, a multi-scale inversion is applied to invert for interface variations of different wavelengths simultaneously. Several measures are devised to establish the reference velocity models and to increase the computation efficiency. Tests with synthetic and field data demonstrated that, in areas of sufficient spatial coverage of shots and receivers, the deformable tomostatics method is able to establish 3D near-surface velocity models of satisfactory quality.