Preconditioning tau tomography with geologic constraints

Robert G. Clapp and Biondo Biondi

bob@sep.stanford.edu, biondo@sep.Stanford.EDU

ABSTRACT

Seismic tomography is a non-linear problem with a significant null-space. Our estimation problem often converges slowly, to a geologically unreasonable model, or not at all. One reason for slow or non-convergence is that we are attempting to simultaneously estimate reflector position (mapping velocity) and image our data (focusiing velocity). By performing tomography in vertical travel-time space, we avoid estimating mapping velocity, instead concentrating on focusing velocity. By introducing anisotropic preconditioning oriented along bedding planes, we can quickly guide the inversion towards a geologically reasonable model. We illustrate the benefits of our tomography method by comparing it to more traditional methods on a synthetic anticline model. In addition, we demonstrate the method's ability to improve the velocity estimate, and the resulting migrated image of a real 2-D dataset.