Improved seismic processing by optimised traveltime approximations

Seismic imaging methods can be separated into time and depth processing. Depth processing is more advanced. Time processing is simpler, cheaper, more robust and widely applied in the industry. Time processing methods represent the kinematics of wave pr opagation by means of simple traveltime approximations. Traveltime approximations are also used by velocity analysis to estimate velocity models that are required by depth imaging methods. Hence, they play a key role for both time and depth seismic proc essing. Unfortunately, the accuracy of existing traveltime approximations decreases with increasing offset, anisotropy and wave conversions. With certain types of anisotropy, and with long-offset surveys (e.g. subbasalt imaging) these approcimations become too in accurate, and preclude the direct use of standard processing methods. Deriving approximations that are accurate at all offsets, whatever the amount of anisotropy and wave conversion, is the first challenge of the project. The second challenge is to deve lop new methods for time processing and velocity analysis that use these approximations and that may replace classical standard processing. The last challenge is to demonstrate the potential of the developed methods by applying them to difficult data set s.