Reverse time migration RTM exhibits great advantagesover other imaging methods because it is based on computingnumerical solutions to a two-way wave equation. It does notsuffer from dip limitation like one-way downward continuationtechniques do, thus enabling overturned reflections to beimaged.As well as correctly handling multipathing,RTMhasthe potential to image internal multiples when the boundariesresponsible for generating the multiples are present in themodel. In isotropic media, one can use a scalar acoustic waveequation for RTM of pressure data. In anisotropic media, PandSV-waves are coupled together so, formally, elastic waveequations must be used for RTM.Anew wave equation for Pwavesis proposed in tilted transversely isotropic TTI mediathat can be solved as part of an acoustic anisotropic RTMalgorithm,using standard explicit finite differencing. If theshear velocity along the axis of symmetry is set to zero, stablenumerical solutions can be computed for media with a verticalaxis of symmetry and not less than . In TTI media withrapid variations in the direction of the axis of symmetry, settingthe shear velocity along the axis of symmetry to zero cancause numerical solutions to become unstable. A solution tothis problem is proposed that involves using a small amountof nonzero shear velocity. The amount of shear velocity addedis chosen to remove triplications from the SV wavefrontand to minimize the anisotropic term of the SV reflection coefficient.We show modeling and high-quality RTMresults incomplex TTI media using this equation.
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