Image stacking versus patching

The images obtained by synthesizing plane waves can be handled in two ways, stacking or patching, according to the purpose of imaging. If one is interested in structure imaging, the stacking of all the images that were obtained by synthesizing different plane waves is helpful because it enhances the image quality by constructive interference where the reflector is and reduces noises by destructive interference. Figure  shows the result of image stacking with thirty-one plane waves synthesized at the surface, where the incidence angle changes from -30 degrees to 30 degrees. Comparing this to the image obtained by synthesizing a single plane-wave at the surface (Figure ), we can see a significant improvement in the quality of reflector images.

On the other hand, if one is interested in the angle-dependent reflectivity recovery or prestack velocity estimation, each image obtained by synthesizing different plane waves should be saved separately because each image contains different information. Even in the image obtained by the synthesis of a plane-wave, only the portion of the image where the plane-wave was synthesized is interpretable because the plane-wave will be distorted after propagation through a complex velocity medium and we do not know the incidence angle of the distorted plane-wave at each depth unless we perform exhaustive ray-tracing. Therefore, I patched the interpretable parts of images obtained by synthesizing a plane-wave at different depths to produce common-incidence angle images. For example, Figure  shows the image obtained by patching twenty-one images obtained by synthesizing plane waves ( 0 degrees ) at twenty-one equi-spaced depth levels. Comparing this to the image obtained by synthesizing a plane-wave at the surface (Figure ), we can observe that the quality of images is almost the same in the entire section, unlike Figure , where the quality of image significantly changes from place to place.

 

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Figure 22 Image obtained by stacking thirty-one plane wave synthesized at surface. Incidence angle at surface changes from -30 degrees to 30 degrees.

 

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Figure 23 Image obtained by patching twenty-one images which are obtained by synthesizing twenty-one plane waves which are equi-spaced in depth.