Combination of common-midpoint-refraction seismics with the generalized reciprocal method |
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| Authors: | Dirk Orlowsky Horst Rüter Lothar Dresen |
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| Institution: | aDMT-FP, GeoTec Division, Geo-Engineering, Franz-Fischer-Weg 61, 44307 Essen, Germany;bRuhr University Bochum, Institute for Geophysics, Universitätsstraße 150, 44801 Bochum, Germany |
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| Abstract: | A useful method for increasing the signal/noise ratio of refracted waves is Common-Midpoint (CMP)-refraction seismics. With this technique the shallow underground can be described in detail using all information (amplitude, frequency, phase characteristics) of the wavetrain following the first break (first-break phase). Thus, the layering can be determined and faults, weak zones, and clefts can be identified. This paper deals with the optimization of CMP-refraction seismics used in combination with the Generalized Reciprocal Method (GRM). Theoretical studies show a close relationship of both methods to the kinematics of wave propagation. Velocities and optimum offsets determined by the GRM can be used directly in the partial Radon transformation in CMP-refraction seismics. The integration of refracted waves leads to an increase in the signal/noise ratio but simultaneously the integration boundaries must be restricted to deal only with selective parts of the investigated refractor. The result of this process is an intercept-time section which can be converted directly to a depth section using standard refraction seismic techniques. Another possibility of depth conversion is the transformation of this intercept-time section to a `pseudo-zero-offset section', known from reflection seismics. Thus, zero-offset sections can be migrated using wave-equation techniques such as Kirchhoff migration. |
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| Keywords: | Refraction seismics Migration Radon transformation Environmental geophysics |
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