When tectonic plates shift, why is there only an earthquake in a single place and not all along the plates’ boundaries?
Friction holds the plates in place without friction they could glide more easily. That being said some areas the has less friction than others and they do slide more easily in that area.
As plates try to shift, the plate becomes locked as rocks on one side catch on rocks on the other side. The plate bends as the forces build up and the catch point gives, and you get an earthquake. This shifts load to other catch points, that might then give – these are aftershocks.
These quakes release the tension in that area of the plates. Another sequence of quakes will happen mearby, releasing tensions in that area. All these small shifts happening over the centuries makes up a shift in the tectonic plates.