I think what is interesting here is that the volcano has no direct connection to the fault moving in the earthquake. The earthquake triggering or influencing to eruption is not part of the volcano’s system of faults with direct relationship with the upward pressure of the magma.
Those waves would be expected to 'break' in subduction zones and under mountainous regions where the plates ride deeper in the mantle, or be reflected and or refracted by such obstacles protruding into the mantle.
If the situation exists, and the angles were right, nodal and 'rogue wave' points should occur as well with those reflected or refracted waves, much as they do in water at the surface.
Consider, too, that the plates are connected, and the relief of stress in one area might translate to a relief of compression or even tension along those plate boundaries in another area as well.
Much of the volcanic activity on the planet is associated with plate margins, so it would be understandable if the stress adjustments among the plates could lead to the compression of (increase in stress on/pressure in) magma chambers or the weakening of lithologic material blocking pre-existing pathways to the surface, or both.