There has been growing interest recently in study the means for modifying material parameters of SAW substrate surfaces in a controllable way. The problem is of considerable practical importance both in relation to optimization of SAW characteristics, especially in a high frequency region, as well as to make them adaptable to changeable conditions. To clearly understood and control these features and for improved device design, it is important to have a reliable theoretical model for dynamical behaviour of substrates with structurally modified near-surface layers. The purpose of this paper is to set forward a systematic approach to model the local changes in elastic and quasielastic parameters as produced by point centres of microdistortion, selectively introduced into the near surface region of some higher symmetry substrates. To make the problem tractable for conditions existing at real surfaces, with a generally complex internal microstructure, the treatment is formulated in terms of a nonlocal theory of elasticity using, locally averaged over microscopic details, multipole material and field characteristic. The method will be illustrated for an impurity-induced realization of a periodic 2D grating composed of clusters of another phase with an externally controlled profile.