The Importance of Anisotropy for Prestack Imaging of Extensional Fault Systems

The presence of anisotropy in the subsurface is a generally accepted but commonly overlooked<br>concept in processing. When it is addressed, usually only the effect on moveout is considered. This<br>paper shows the importance of including anisotropy in imaging, not only because it properly handles<br>the long offset moveout but also because it correctly handles the focusing and spatial positioning<br>which is subtler but may be even more important. The paper shows an imaging problem from the<br>coast of the Gulf of Mexico. It is a problem involving fault related rollover structures that are<br>common worldwide. The fundamental aspects of anisotropy in imaging are introduced. Then the<br>impact of anisotropic prestack time migration on this example is shown along with a practical strategy<br>for its implementation. The impact is demonstrated using sections and time slices from the 3D survey<br>comparing previous processing without anisotropy to new processing with anisotropy. The<br>anisotropic prestack time migration properly focuses and images the complex growth fault structures<br>and leads to significantly higher spatial resolution of the targets.