Lithospheric plates are subducted episodically, a few meters at a time, during earthquakes. These earthquakes recur over intervals ranging from decades to centuries. Within weeks to perhaps years after such an earthquake, elastic stresses induced in the asthenosphere relax, allowing displacement and stress to propagate away from the subduction zone into the adjacent plates. Finite element modelling of this process has shown that the propagation is asymmetric, the subducted slab serves to buffer the subducting plate against extensive motion. We have constructed a simple analytic model which incorporates the effect of the subducted slab in a fundamental way. The slab's effect is modelled by a Maxwell viscoelastic element which is attached to the subducting plate. Both plates obey Elsasser's displacement propagation equations. The elastic response of the Maxwell element at first restrains the motion of the subducted plate. The plate eventually moves on the timescale of stress relaxation in the Mesosphere (hundreds to thousands of years). The model predicts that the trench moves toward the subducting plate at an average speed of one half of the convergence rate. A strong extensional pulse is propagated into the overthrust plate shortly after the earthquake, whereas the stress pulse is small in the subducting plate. Although this extension changes into compression before the next earthquake in the cycle, the period of strong extension following the earthquake may be responsible for extensional tectonic features in the back-arc region.