Traveltime Tomography in Isotropic and Transversely Isotropic Media

Marco A. Perez

This thesis builds two types of velocity models through crosswell and surface experiments using traveltime tomography. One is isotropic, consisting of estimating P-wave velocities, and the other is transversely isotropic, estimating Thomsen's weak anisotropy parameters of , and .

Traveltimes are modelled using a finite-difference scheme in simple isotropic and transversely isotropic models and used to determine tomographic resolution capabilities for crosswell and surface geometries. Results show that crosswell tomography can accurately detect vertical velocity variations as well as provide a reasonable estimate for while surface tomography can accurately detect horizontal velocity variations and provide a reasonable estimate for .

Two different quasi-null space inversion stabilization techniques are also introduced in this thesis. The first stabilizes the inversion result by smoothing unreliable results while the second integrates two different seismic experiments based on their relative reliability. Results show that tomogram accuracy is improved when using these two techniques.