Seismic imaging is a technique that uses seismic echoes to map and detect underground geological structures. The conventional seismic image has the resolution limit of λ/2, where λ is the wavelength associated with the seismic waves propagating in the subsurface. To exceed this resolution limit, this thesis develops a new imaging method using resonant multiples, which produces superresolution images with twice or even more the spatial resolution compared to the conventional primary reflection image.
A resonant multiple is defined as a seismic reflection that revisits the same subsurface location along coincident reflection raypath. This reverberated raypath is the reason for superresolution imaging because it increases the differences in reflection times associated with subtle changes in the spatial location of the reflector. For the practical implementation of superresolution imaging, I develop a poststack migration technique that first enhances the signaltonoise ratios (SNRs) of resonant multiples by a moveoutcorrection stacking method, and then migrates the poststacked resonant multiples with the associated Kirchhoff or waveequation migration formula. I show with synthetic and field data examples that the firstorder resonant multiple image has about twice the spatial resolution compared to the primary reflection image.
Besides resolution, the correct estimate of the subsurface velocity is crucial for determining the correct depth of reflectors. Towards this goal, waveequation migration velocity analysis (WEMVA) is an imagedomain method which inverts for the velocity model that maximizes the similarity of common image gathers (CIGs). Conventional WEMVA based on subsurfaceoffset, angle domain or timelag CIGs requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, I present a new WEMVA method using planewave CIGs. Planewave CIGs reduce the computational cost and memory storage because they are directly calculated from prestack planewave migration, and the number of plane waves is often much smaller than the number of shots. In the case of an inaccurate migration velocity, the moveout of planewave CIGs is automatically picked by a semblance analysis method, which is then linked to the migration velocity update by a connective function. Numerical tests on synthetic and field datasets validate the efficiency and effectiveness of this method.
Date of Award  Aug 28 2017 

Original language  English (US) 

Awarding Institution   Physical Science and Engineering


Supervisor  Gerard Schuster (Supervisor) 

 Superresolution
 Seismic Imaging
 Plane Wave
 Migration Velocity