Location where the different magnitude eathquakes typically occur?

Earthquakes come about when pent-up frictional energy in the earth's crust is suddenly released.

Usually the build-up of the energy comes about due to friction between different plates of the earth's crust, boundaries that we sometimes term Fault Lines. Two plates get wedged together, the pressure builds up and BANG! - it releases suddenly in an earthquake.

This release can be little-and-often (small magnitude quakes) or in one huge and highly destructive quake.

Here's a map of earthquakes since 1900 that have equalled or exceeded Magnitude 8.0:

http://earthquake.usgs.gov/earthquakes/eqarchives/...

All are close to plate boundaries and most are on the Pacific Rim.