Depth imaging with reflection statics derived from model-based moveout
Dennis K. Ellison
In land reflection seismic data analysis, reflection static corrections are analytical solutions for resolving timing differences between measured and theoretical arrival times of seismic waves. These static corrections can make a substantial difference in the absence of detailed nearsurface information and are dependent on assumptions associated with the normal moveout (NMO) theory. NMO is an analytical solution based on the assumption that the moveout in seismic data can be approximated by an hyperbola. This assumption is valid when the moveout pattern is near-hyperbolic but fails when it is not. Scenarios where moveout is not hyperbolic include situations: when the topography is not flat; when strong lateral velocity variations are present; when there are strong variations in velocity magnitudes and seismic weathering thickness across the data.
A moveout velocity field can be created using raytraced traveltimes from the velocity model instead of NMO. These traveltimes are calculated from each source and receiver and can be applied to the respective traces at the corresponding offset. This model-based moveout (MMO) correction is coupled to depth migration and allows for asymmetric non-hyperbolic moveout commonly associated with strong lateral velocity variations in the subsurface. These MMO derived static corrections can render sharper depth migrated images and lead to stronger geologic representation of the depth imaging velocity model.