A diffraction theory

Notice that this is not a ray theory nor a plane-wave theory, and certainly not a dynamic elastic wave theory. It does correspond to notions with which explorationists are familiar, and only uses (no v(z)!) parameters that can be estimated at the surface. Also note that this is not, despite appearances, just a horizontal reflector theory. A kinematic diffraction theory develops by combining half reflections from the same layer set but with differing ray parameters for the up- and down-going waves. In other words, there are now two independent ray parameters, p_s and p_g, and development follows most simply by considering a source-to-scatterer-to-receiver model.