The computational tools for imaging in transversely iso-tropic media with tilted axes of symmetry (TTI) are complexand in most cases do not have an explicit closed-form repre-sentation. Developing such tools for a TTI medium with tiltconstrained to be normal to the reflector dip (DTI) reducestheir complexity and allows for closed-form representations.The homogeneous-case zero-offset migration in such a medi-um can be performed using an isotropic operator scaled bythe velocity of the medium in the tilt direction. For the nonze-ro-offset case, the reflection angle is always equal to the inci-dence angle, and thus, the velocities for the source and re-ceiver waves at the reflection point are equal and explicitlydependent on the reflection angle. This fact allows for the de-velopment of explicit representations for angle decomposi-tion as well as moveout formulas for analysis of extended im-ages obtained by wave-equation migration. Although settingthe tilt normal to the reflector dip may not be valid every-where (i.e., on salt flanks), it can be used in the process of ve-locity model building, in which such constrains are usefuland typically are used.
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