Ray and finite-difference modelling of CDP seismic sections for shallow lignite deposits

Johana Brokesova , Jiri Zahradnik & Paraskevas Paraskevopoulos


Numerical experiment oriented to partial validation of the structural model at Domenico lignite site is presented. The structure is 2D and contains several lignite seams at different depths and a low-velocity layer on the top of the model. The experiment consists in simulation of CDP section along one 625 m long segment of the measured profile at the site. The CDP stack was modelled by two independent calculation techniques, based on completely different concepts: the finite-difference method and the ray method. Due to incompletness of the ray synthetic wave field as well as numerical problems of finite-differences at higher frequencies, there is a very poor agreement between the seismogram sections obtained by the two methods for individual shot points. On the other hand, the CDP stacked sections modelled by the ray and finite-difference methods agree rather well. This is because the main differences between the wave fields computed by the two methods are due to the presence of the low-velocity layer (ground roll, multiple reflections, etc.). These parts of the wave field can be suppressed by a routine data processing like f-k filtration and CDP stack for a multi-shot experiment. This is also why the synthetic ray and finite-difference CDP stacks agree relatively well the observed data.

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In: Seismic Waves in Complex 3-D Structures, Report 7, pp. 375-397, Dep. Geophys., Charles Univ., Prague, 1998.