According to the theory of plate tectonics, the Earth's crust is broken into about 12 plates that float on hotter, softer rocks in the underlying mantle. The Earth's internal heat drives convection currents in the asthenosphere, moving the plates past one another very slowly. Plates move only inches each year, carrying the continents and ocean basins with them as they drift.
The majority of earthquakes worldwide occur at all but one location. That is