Amplitude preserving Kirchho migration: A traveltime based strategy

Amplitude versus oset information is a key feature to seismic reservoir characterization. There-fore amplitude preserving migration was developed to obtain this information from seismic re ection data. For complex 3-D media, however, this process is computationally expensive. In this paper we present an ecient traveltime based strategy for amplitude preserving migration of the Kirchho type. Its foundation is the generation of rst and later arrival traveltime tables using a wavefront-oriented ray-tracing technique and a generalized moveout relation for 3-D heterogeneous media. All required quantities for the amplitude preserving migration are computed from coarse gridded travel-time tables. The migration includes the interpolation from the coarse gridded input traveltimes onto the ne migration grid, the computation of amplitude preserving weight functions, and, optionally, the evaluation of an optimized migration aperture. Since ray tracing is employed for the traveltime computation the input velocity model needs to be smooth, i.e., spatial velocity variations below the wavelength of the considered re ection signals are removed. Numerical examples on simple generic models validate the technique and an application to the Marmousi model demonstrates its potential to complex media. The major advantages of the traveltime based strategy consist of its computa-tional eciency by maintaining sucient accuracy. Considerable savings in storage space (105 and more for 3-D data) are achieved. The computational time for the stack is substantially reduced (up to 90 % in 3-D) if the optimized migration aperture is used