Reverse-time migration in TTI media

There is increasing need to perform migration with anisotropic velocity models. Reverse-time migration clearly is more computer resources demanding compared to other migration methods. Therefore, to accelerate computations, the anisotropic elasto-dynamic equations of motions are often simplified to account for qP-wave propagation only in, e.g., TTI media. This reduces the computational effort considerably. However, these so-called pseudo-acoustic wave equations show numerical instabilities if the orientations of the symmetry axes inside the medium do not coincide. Such modeling schemes are not useful for situations where structural changes of the anisotropy occur. However, using a true anisotropic modeling scheme allows reverse-time migration without these restrictions. qPwaves only propagation as with pseudo-acoustic wave equations is possible as well. Synthetic examples of reverse-time migration calculated using the 2D Fourier-method demonstrate the method’s ability to cope very well with arbitrary orientations of symmetry axes.