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3D tomographic velocity model estimation with kinematic wavefield attributes
- Source: Geophysical Prospecting, Volume 52, Issue 6, Nov 2004, p. 535 - 545
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- 02 Nov 2004
Abstract
A tomographic inversion method is presented that uses kinematic information in the form of zero‐offset traveltimes and kinematic wavefield attributes (first and second spatial traveltime derivatives) to determine smooth, laterally inhomogeneous 3D subsurface velocity models for depth imaging. The kinematic wavefield attributes can be extracted from the seismic prestack data by means of the common reflection surface (CRS) stack. The input for the tomography is then taken from the resulting attribute volumes at a number of pick locations in the CRS stacked zero‐offset volume. As a smooth model description based on B‐splines is used and reflection points are treated independently of each other, only locally coherent events in the stacked volume are required and very few picks are needed. Thus, picking is considerably simplified.
During the iterative inversion process, the required forward‐modelled quantities are obtained by dynamic ray tracing along normal rays pertaining to the input data points. Fréchet derivatives for the tomographic matrix are calculated with ray perturbation theory. The inversion algorithm is demonstrated on a 3D synthetic data example, where the kinematic wavefield attributes have directly been obtained by forward modelling.