3D CRS-Based Velocity Model Building - An Accurate and Cost-Effective Approach

The resolution of first arrival traveltimes tomography is limited by the size of the first fresnel zone for each ray, the experimental device and the structure studied itself. This leads to uneven ray coverage and locally varying resolution. Besides, the sensitivity kernel of each ray induce high frequency information even where theoretical resolution is poor.Smoothing constraints are often added to the tomographic system to deal with these problems. We propose an alternative adaptive parametrization based on second generation wavelet transform, as introduced by Wim Sweldens.<br><br>We explain the principles and interesting properties of wavelet transform and show how we insert it in the tomography process. Then we present a synthetic example showing difficulties generated by rays in velocity model recontruction. We present the effects of classical gaussian smoothing and of our adaptive parametrization using wavelets.We show that wavelet transform allows a better control of the resolution power depending on the parameter location and that it is more adaptive than classical methods.