Sparse norm reflection tomography for handling velocity ambiguities

Reflection seismology with the normal range of offsets encountered in seismic surveys is unable to resolve all the wavelength components of the subsurface velocity. One approach for overcoming this difficulty has been to drive the velocity determination towards models which make Geological sense. The assumption behind this study is that the velocities within subsurface layers tend to be smooth, excluding isolated areas where they can vary discontinuously. For accommodating this assumption we use a tomographic velocity determination method which is based on a Cauchy sparse norm and a representation of the parameters in the wavelet transform domain. The sparse tomography method is compared to conventional tomography in a synthetic example and a field data example. In general the sparse inversion produced superior results. In a second field data example, the new method is used for resolving artifacts caused by irregularities in the near surface as a result of permafrost.