Next: Chapter 2: PS imaging
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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.