How does Earthquake work?

Basically, the earthquake is the result of energy released immediately when the hit of convention moving in the asthenosphere. Therefore, the plates are move at the region where the energy release. Thus, we can feel earthquakes.

Originally, there are three types of plate movement in the earthquakes. According to the direction of plate movement, they are Normal, Thrust, Strike-slip.

Normal earthquake works in a plate movement of normal condition.
That means both of two plantes allow the gravitation
to move on fault plane.

Thrust earthquake is different from Normal earthquake. It works in a unnatrual way which means both of plates don't allow the gravitation to move on fault plane. Therefore, thrust earthquakes need more energy than normal earthqake to happen and thrust earthquake usually makes more seriously consequence than normal earthquake.

Strike-slip earthquake are different from Normal and Thrust. Strike-slip earthquake works in a horizontal line. One plate moves forward but the other plate moves backward.

Reference:http://en.wikipedia.org/wiki/Earthquake#Naturally_occurring_earthquakes