Joint inversion modelling in borehole geophysics

For a healthy geophysical assessment, compatibility and unconformity between subsurface models is important. Discrete inversion models of various geophysical methods can produce different and precise results for the same subsurface structures. In these thesis, inverse solution models obtained from different geophysical methods in the same model network was interpret together. For this purpose, Matlab based forward solution algorithms related to borehole electrical resistivity and seismic transmission tomography methods have been produced. "Res2BH-FW" program has been developed for the electrical resistivity tomography method. Sensitivity distributions of four-electrode measurement protocols were compared for a homogeneous model. A four-electrode borehole electrical resistivity measurement protocol, which is expected to produce the most suitable underground model with the least data set for complex underground structures, was proposed. "Ray2BH-FW" program has been produced for seismic transmission tomography method. BH2D-INV and BH2D-JointINV programs have been developed, which can make the discrete and joint inversion of both methods, respectively. The joint and discrete inverse solution results were compared in the complex subsurface models. In these comparisons, the data and model misfit values of the inversion results were examined. The results of inverse-solution models closer to the true model were obtained in this study with appropriate initial models related to geological structures. As a result, it has been understood that the electrical resistivity model result, which has more artificial distribution, has been improved by seismic transmission tomography. In this context, it has been revealed that the joint inversion results of electrical resistivity and seismic transmission methods are more successful than the discrete inversion in determining of complex underground structures.