Interpretation of shallow refraction seismic data by reflection/refraction tomography |
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| Authors: | Pavel Ditmar Jan Penopp Rainer Kasig & Jannis Makris |
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| Institution: | Hamburg University, Institute of Geophysics, Bundesstrasse 55, 20146 Hamburg, Germany.,; Present address: Utrecht University, Institute of Earth Sciences, Department of Geophysics, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. |
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| Abstract: | A new algorithm for tomographic inversion of traveltimes of reflected and refracted seismic waves is developed. The inversion gives interface configurations and velocity distributions in layers. The important features of the algorithm are: (a) the inclusion of shot time delays in the list of unknown parameters; (b) the regularization is applied in such a way that the most probable model is characterized by the similarity of neighbouring interfaces. As the problem under consideration is non-linear, several iterations are necessary in order to obtain the final model. In the case of a very inexact initial model, a 'layer-by-layer' inversion strategy is recommended as a first inversion step. The inversion program is supplied with a user interface, thanks to which one can: (a) pick interactively and identify seismic traveltimes; (b) build and edit depth/velocity models; and (c) display calculated traveltime curves and compare them with picked traveltimes as well as with the original seismic sections. The efficiency of the inversion software developed is illustrated by a numerical example and a field example in which shallow seismic data are considered. Application to wide-aperture reflection/refraction profiling (WARRP) data is also possible. |
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