How is the location of earthquakes across the globe related to the location of volcanoes?
From my Geology Memory Lane!
When I studied Plate Tectonics I remember that my teacher told me that continuously plates are in movement in particular entering one inside, or better, below another. This kind of movement not only produces fissures in the plate from where magma can reach the surface but also grinding that causes earthquakes!
Plate 2, in figure, is pushed against plate 1 getting deformed in the process (like pushing a sheet of paper against an obstacle, it forms a bump). During the deformation fissures can appear due to this deformation and magma, from the melting of plate 1 underneath it, can channel to the surface. Plate 2 grinds against plate 1 and can "get stuck" during the movement; it then can free itself and move suddenly producing an earthquake.