  In this paper, a systematic study of the strong metric subregularity property
of mappings is carried out by means of a variational tool, called steepest
displacement rate. With the aid of this tool, a simple characterization of
strong metric subregularity for multifunctions acting in metric spaces is
formulated. The resulting criterion is shown to be useful for establishing
stability properties of the strong metric subregularity in the presence of
perturbations, as well as for deriving various conditions, enabling to detect
such a property in the case of nonsmooth mappings. Some of these conditions,
involving several nonsmooth analysis constructions, are then applied in
studying the isolated calmness property of the solution mapping to
parameterized generalized equations.
