Pre-stack Time Migration (PSTM)
PSTM is an excellent imaging tool in situations where strong
or very complex subsurface velocity fields are not expected. New
implementations are capable of imaging very steep dips in excess
of 90°.
PSTM gathers are still the industry standard for AVO
and attribute work. Their reliability, speed and robustness
can compensates for the simplifying assumptions used.
An anisotropic version using the Hake approach is also available.
Kirchhoff
Pre-Stack Time Migration (KPSTM)
KPSTM is a full Kirchhoff diffraction summation algorithm that
includes advanced anti-aliasing filters and is capable of imaging
turning waves.
Depending on the vertical changes in velocity, KPSTM can be used
in several ways, from a 6th-order anisotropic curved-ray approximation
to a full ray-traced solution capable of imaging dips greater
than 90°, including salt overhangs.
Anisotropic
PSTM (A-KPSTM)
A-KPSTM is based on our successful KPSTM with
anisotropic correction terms included. A unique feature of this
implementation is the ability to account separately for the large
offset effects (6th order) and the true earth anisotropy by using
the Hake approximation.
 Case Study: Turning Ray Prestack Time Migration with Raytraced Offset-Dependent Velocities (presented at SEG, September 2007)
 Extended Curved Ray Prestack Time Migration (PSTM)
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