| 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 alpha, epsilon and delta.; 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 epsilon while surface tomography can accurately detect horizontal velocity variations and provide a reasonable estimate for delta.; 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. |
