ABSTRACT: Wide-band Fresnel zone wavepath tomography and its application to crosswell and land seismic refraction imaging

We introduce a new algorithm for Fresnel zone wavepath inversion that considers wide band wave spectra. The frequency parameter used in this inversion method sweeps from low to high frequencies. With this sweeping frequency procedure, the inversion starts from a large and smooth anomaly and follows gradually to the finer and sharper anomaly. Using this strategy, we can obtain a more accurate estimation and wide angle in reconstruction. In this paper, the application of this method in the case of crosswell tomography and horizontal source receiver configuration are presented. The model studies are shown that applying this method to the crosswell tomography provides robust inversion in both dense and sparse data, and also wide angle reconstruction. This method also provides stable inversion in land seismic refraction tomography. Where, the problem in applying tomography to the land seismic refraction method is the ambiguity of velocity and depth, it is caused by sources and receivers lie in the same depth (zero aperture angle). To handle this problem, an initial model which close to the true model is absolutely required, or the position of refractor depth should be defined accurately. Here, the propose method of land seismic refraction tomography method using wide-band Fresnel zone wavepath tomography can handle the above problem. The refractor is imaged correctly eventhough using the homogeneous initial model determined from direct wave. In addition, it still provides faster computation than raypath tomography within the grabens.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia