Higher-order Dynamic Ray Tracing for Extrapolation of Traveltime and Geometrical Spreading
E. Iversen, B. Ursin and M.V. de Hoop
Event name: 80th EAGE Conference and Exhibition 2018
Session: Seismic Modelling I
Publication date: 11 June 2018
Info: Extended abstract, PDF ( 501.88Kb )
Price: € 20
Dynamic ray tracing is an efficient and reliable method for computation of geometrical spreading along a given reference ray. The method yields first-order derivatives of perturbations in position/slowness and therefore enables first-order extrapolation of these quantities to points in the close (paraxial) neighbourhood of the reference ray. Knowledge of such first-order perturbation derivatives readily gives coefficients for second-order extrapolation of traveltime into the paraxial region. We have extended conventional dynamic ray tracing for anisotropic media to include continuation of higher-order perturbation derivatives along the reference ray. The motivation is to provide a robust and non-trivial extrapolation of geometrical spreading and other amplitude-related quantities to paraxial points. Important by-products of the method are coefficients for higher-order expansion of traveltime. Volumetric properties of the medium are represented using quintic (fifth-order) B-spline functions. We have tested the method using a 3D isotropic model with weak lateral heterogeneities. For this model, fourth-order extrapolation of traveltime and third-order extrapolation of paraxial position gave results of high accuracy.