In layman’s terms an earthquake occurs when two blocks of the earth slip. This slip surface is called a fault or fault plane.
- Classification of the type of fault uses the angle of the fault with respect to the surface (Dip) and the direction of slip along the fault.
- Faults moving along the direction of the dip plane are dip-slip faults and can be either normal or reverse, depending on their motion.
- Faults that move horizontally are called strike-slip faults and can be either right or left lateral.
- Some faults have both dip-slip and strike-slip motion and are called oblique-slip faults.
Where the earthquake originates below the surface is known as the hypocenter and the location directly above on the surface is known as the epicenter.