How earthquakes happen
This is a digram of how earthquakes happen. The red dot in the middle is the focus, that where it all starts when an earthquake happens, where the ground shakes in this spot and send out waves outward all directions like when a pebble drops in the middle of a bucket filled with water, it sends out ripples. Another thing that helps causing earthquakes is the fault, a crack in earth crust where the sorrounding rock has moved or shifted. The epicenter has it's role but it's role doesn't help much it's really just the middle of the earthquake. The fault scarp is a small step on the ground suface where one side of the fault has moved vertically with respect to another.