Transmission properties of a plane fault

Continuity conditions are derived for a fault modelled as a plane with isolated areas of slip. These slip areas are, for simplicity, taken to be such that their overall effect is that of a distribution of circular cracks; discontinuities in both normal and tangential components of displacement are allowed, depending on the internal conditions. Dry (gas-filled), partial or saturated liquid fill, or a fill of a weak visco-elastic solid are possible within the theory. The results are given in terms of the mean wave, which, at wavelengths long compared with the scale-lengths of the fault structure, is an accurate approximation to the displacement field. The continuity conditions that arise under this scheme are identical to those for a thin layer of visco-elastic material. However, unlike earlier, more empirical models of an 'averaged' fault, the parameters involved are directly related to the fault structure and include crack-crack interactions. It is clear from earlier work that a fault of this type is capable of supporting Stoneley waves.