The determination of converted-wave statics using P refractions together with SV refractions

Armin W. Schafer

ABSTRACT

In order to improve the static solution of converted (P-SV) wave data recorded on the radial channel of three-component seismic surveys, shear-wave refractions are used to obtain a model of the near-surface velocities and thicknesses for shear waves, in the same way that P-wave refractions have been used previously. The static shifts due to shear waves are then calculated using ray-tracing. By combining the receiver terms of the shear-wave statics solution with the source terms of P-wave statics solution, the statics solution for converted waves using P-wave and SV-wave refractions, also referred to in this report as the 'P-SV refraction statics solution', is obtained. Any noticeable, large static shifts remaining after application of this method are then readily removed using common-receiver stacked sections. Using an automatic residual statics program on the data then results in a final section with most of the statics shifts removed.

Two static-removal methods, hand-picking and P-SV refraction statics, are applied to the radial component of a compressional-source, three-component, seismic data set from northern Alberta; Slave Lake, Line EUE001. The amount of time required for the entire process is similar for the two methods; however, the resolution and continuity of reflections is improved using the P-SV refraction statics solution. Further, since the P-SV refraction statics solution derives long-wavelength static shifts from an actual model of the Earth, rather than by comparing the shifts seen on reflections across the section, the P-SV refraction statics solution provides a more realistic long-wavelength statics solution. The advantage of using P-SV refraction statics is that the final product is greatly improved, without any increases in processing time required.

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