Target-oriented wave-equation inversion: regularization in the reflection angle

Abstract:

A complex velocity model produces shadow zones in an image due to focusing and defocusing of the seismic waves, and limited recording geometry. These shadow zones contain weak signal masked by artifacts. To recover the real signal, and reduce artifacts is necessary to go beyond migration. One option is to use a wave-equation target-oriented inversion scheme that explicitly computes the least squares inversion Hessian. The wave-equation target-oriented inversion has a big null space. It seeks to form an image where there is lack or very little data information. In this situation is where a priori information in the form of model regularization can help to stabilize the results. One choice for regularization, that makes physical sense, is to force the inverse image to be smooth with the reflection angle. It works by spreading the image from well illuminated to poorly illuminated reflection angles. In order to impose this smoothness constraint I implemented a chain of the subsurface-offset Hessian and a slant-stack (reflection angle to subsurface-offset) operator. Results on the Sigsbee synthetic model show that the inversion regularized in the reflection angle reduces the effect of the uneven illumination not only in the angle gathers but also in the stack image.

Target-oriented wave-equation inversion: regularization in the reflection angle