Radon methods for improved imaging of high-velocity layers using mode-converted energy

Shauna Kaye Oppert

ABSTRACT

Weak-amplitude P-wave reflections and coherent-noise problems generated from mode-converted waves inhibit seismic imaging in high-velocity fields. Accurate velocity models, adequate acquisition parameters, and advanced migrations can produce reasonably accurate images of the subsurface in some cases. Radon-transform techniques designed to localize mode-converted waves provide alternative methods for improved imaging of this data. Sophisticated summation curves are employed in the algorithms to enhance the focusing capabilities of nonhyperbolic reflections in Radon space and to improve coherent-noise suppression. The t2-stretched transforms and high-resolution Radon variants are suited for muting amplitude-increasing events, including modeconverted waves. Standard parabolic and hyperbolic Radon transforms typically involve smearing of reflections across Radon space, which reduces the effectiveness of coherentnoise suppression. The shifted-hyperbolic Radon transform employs a curve-fitting technique to allow for flexibility in predicting the true moveout of specific reflections The shifted-hyperbolic equation exhibited superior performance over the parabolic and hyperbolic transforms at minimal computational cost.

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