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Are refraction attributes more useful than refraction tomography?
- Source: First Break, Volume 28, Issue 7, Jul 2010,
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- 01 Jul 2010
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Abstract
A seismic attribute is any measure that helps to better visualize or quantify features of interest in seismic data. Several refraction attributes, in addition to seismic velocity, can be readily computed from the first arrivals in seismic data. Refraction attributes can be usefully employed in the geotechnical characterization of the near surface. The major effect of tomography is largely cosmetic because it rarely improves resolution. Numerous refraction tomograms, which range from the geologically improbable to the very detailed, can satisfy the travel time data to sufficient accuracy. In the initial or reconnaissance stage, refraction attributes can be used to compute detailed starting models and to resolve non-uniqueness inherent in refraction tomography. Whereas refraction tomography non-uniquely models the single attribute of seismic velocity, this study demonstrates that the additional model parameters of scaled density ratio and P-wave modulus strength can be readily computed from combinations of refraction attributes. The spatially extensive refraction attributes can then be integrated with quantitative borehole and other geotechnical data using multivariate geostatistics. It is concluded that more useful quantitative geotechnical models of the near surface can be obtained by employing a wider range of attributes than the seismic velocity alone.