Fault Types

Fault is a fracture or crack where two rock blocks slide past one to another. If this movement may occur rapidly, it can be causes earthquike or slowly, in the form of creep. Types of faults include strike-slip faults, normal faults, reverse faults, thrust faults, and oblique-slip faults. It can be small and large complex interconnection fault systems and can replace one type of fault in one location with another type in another. Many faults are associated with folds. Faults are separated, bifurcated, converge, or move away from distances, sometimes creating complex fracture systems.

The relative motion of faults (one side to the other) is described in terms of relationship of a hanging wall and foot wall.

A foot wall is a block under a fault with a sloping fault plane.

A hanging wall is a block (rocks) at the top of a sloping fault plane.

It is simply described here – if a fault plane is exposed well enough to see that it is inclined, the side on which you can stand is called the foot wall. The side where you can hang your feet without touching the floor is the hanging wall.

There are three types of dip-slip faults: normal, reverse, and thrust.
The character of the movement (offset) along the fracture plane determines what kind of dip-slip fault it is.

faults and folds

If the rock mass on a sloping fault moves downward, the it is normally called reverse if the rock above the fault moves upward. An inverse fault in which the fault plane is inclined at an angle equal to or less than 45 ° is called a pressure fault.

A normal fault appears to be that the suspended wall moves downward relative to the foot wall. The dip angle of the sliding surface is between 45 and 90 degrees. Many normal faults in mountainous regions are caused by gravity along the edges of the mountains and may be associated with elevation of the head wall of the slums.

A reverse fault, which the hanging wall moves upward relative to the foot wall.

A thrust fault is an dip angle of 45º or less to the extent that the suspended wall appears to move upward relative to the foot wall. Horizontal compression or rotation shift is responsible for displacement.

A strike-slip fault is a generally vertical fault where the two sides pass horizontally past each other. If the block opposite an observer facing the fault moves to the right, the shift style is called “right lateral.. If the block moves to the left, the movement is called “left lateral.. The San Andreas Fault in California is the most famous example of a right lateral impact-slip fault. It produces a variety of floor shapes including pulse shifts, louver ridges, detachable basins, overhanging pools and deflected streams.

Oblique slip faults show important components of both horizontal (impact-slip) and vertical (slip-shift) motion. The oblique slip error combines the impact-slip motion with significant normal, reverse or push slip.