Earthquakes occur all the time all over the world, both along plate edges and along faults. Most earthquakes occur along the edge of the oceanic and continental plates. The earth's crust (the outer layer of the planet) is made up of several pieces, called plates.
So, where do deep earthquakes occur most often?
The deepest earthquakes occur within the core of subducting slabs - oceanic plates that descend into the Earth's mantle from convergent plate boundaries, where a dense oceanic plate collides with a less dense continental plate and the former sinks beneath the latter.
Which plate boundary has the largest earthquakes?
At convergent plate boundaries, where two continental plates collide earthquakes are deep and also very powerful. In general, the deepest and the most powerful earthquakes occur at plate collision (or subduction) zones at convergent plate boundaries.