next up previous print clean
Next: Chapter 2: PS imaging Up: Introduction Previous: Problem description

Thesis Overview

This dissertation focus on several problems with processing and imaging of the converted-wave section of OBS seismic data. First, the CMP to CCP/CRP transformation, although there are several methods that approximate this transformation, many of them assume an Earth's subsurface structure conformed by flat layers and constant velocity. The second problem is the polarity-flip correction, conventional process flips the polarity for the negative offsets in all the common shot gathers. I propose a solution that actually uses the polarity flip to indicate the accuracy of the subsurface image. Finally, I address the irregularity in the 3-D acquisition geometry, I use a new method for converted waves that utilizes an imaging operator designed to handle converted-wave data. The final solutions for these three problems are composed of an image which dimensions are depth, image-midpoint location, and subsurface-offset location.

Imaging is the combined process of migration and velocity analysis. The final image provides information on the structure of the Earth's subsurface and it should also yields estimates for the P and S velocity models. This problem is non-linear in nature. To obtain a reliable image, we need a reliable velocity model. This thesis is divided into four main chapters. Chapters 2 and 3 address 2-D problems in the PS portion of the OBS seismic data. Chapters 4 and 5 focus on 3-D PS OBS seismic data. I will give a brief summary of the main points and conclusions for each of these chapters.