1887

Abstract

Hyperbolas are a widely observed feature in radar reflection data. Zero-offset migration of these hyperbolas rarely improves the image. Often energy is sme~red out and weak reflections disappear. The reasons are perturbations in the local geology influencing the velocity field, uncertainties introduced by uneven movement of the antennas, the bistatic character of the antenna as well as the geometry of the buried objects. In this work the target geometry is incorporated into migration to improve the subsurface image. An algorithm is presented, which automatically determines the diameters of buried pipes without prior knowledge of the medium-velocity for electromagnetic propagation. In a second step the algorithm utilizes these determined diameters of the buried pipes to enhance the radar image through migration. Conventional migration (KIRCHHOFF, f-k, FD) reconstructs the geometry of subsurface features from one parameter alone: the velocity field. Eccentricity-migration incorporates another parameter into migration: the deviating eccentricity of the hyperbola. Therefore, we chose the name "eccentricity-migration". The reflection image of a line diffractor in a radargram is uniquely characterized by its numerical eccentricity N E = V2, the ratio of the focal length of the hyperbola to the apexto- origin distance. For a pipe, N E is smaller than V2. Therefore, if the temporal and spatial resolution of the data are sufficient and changes in medium-velocity are small, then the pipe-diameter can be uniquely extracted from the shape of the reflection hyperbola alone. A further advantage of E-migration is its increased sensitivity to changes in velocity. Based on a known pipe-geometry, either a priori or extracted through E-migration, a more detailed velocity field can be derived and the subsurface image in the vicinity can be furthermore improved.

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/content/papers/10.3997/2214-4609-pdb.300.53
1994-06-12
2021-11-29
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.300.53
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