An interferometric solution for raypath-consistent shear wave statics

Raul Cova, David Henley, and Kris Innanen

ABSTRACT

Converted-wave data processing requires the computation of shear-wave statics for the receiver side. Conventionally this is done under the assumption of surface consistency. However, if the velocity change between the low velocity layer (LVL) and the medium underneath is smooth, the vertical raypath assumption that supports the surface consistent approach is no longer valid. This feature results in a non-stationary change of the statics that needs to be addressed in order to properly solve the problem. In this paper the radial-trace (R-T) transform is used for moving the data to a raypath consistent frame-work where the statics change was showed to be approximately stationary. In this domain traveltime interferometry was applied to retrieve the delays caused by the near surface. Cross-correlation of the delayed traces with a model trace free of statics was showed to return a cross-correlation function that carries the statics information. These functions were convolved with the original traces to remove the delay caused by the near surface. Since all the operations are done in the R-T domain an inverse radial trace transform was applied to return the data to the space-time domain. Stacked sections computed using surface-and raypath-consistent solutions showed how the latter one effectively removed the statics by addressing the non-stationarity of the problem. The analysis of the trend of the cross-correlation functions for different receiver locations showed that there is a link between the delays captured by these functions in the R-T domain and the traveltimes through the near surface at different raypath angles. Such information could be used in an inversion algorithm to retrieve a velocity model for the near surface.

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