What are the different parts of Faults?

Faults are well-defined cracks along which the rock-masses on either side have relative displacement. The attitudes of faults are defined in terms of their strike and dip. The strike and dip of a fault are measured in the same way as they are for bedding.

Description:

The followings are the parts of a fault:

(i) Footwall and hanging-wall:

Of the two blocks lying on either side of the fault-plane, one appears to rest on the other. The former is known as hanging-wall side whiles the latter which supports the hanging-wall is known as the footwall side.

(ii) Fault scrap:

The relative displacement on either side of the fault line results in an upstanding structure with a steep side which is called ‘fault scrap’.

Fault-line scrap:

It owes its relief due to differential erosion along a fault-line.

(iii) Down thrown side and up-thrown side:

In case of a fault, one of the dislocated blocks appears to have been shifted downwards in comparison with the adjoining block lying on the other side of the fault-plane. The former, therefore is known as the down-thrown side while the latter is described as the up-thrown side.

Terminologies associated with faults:

1. Strike:

Strike of the fault is the trend of a horizontal line in the plane of the fault.

2. Dip:

Dip is the angle between a horizontal surface and the plane of the fault and is measured in a vertical plane that strikes at right angles to the fault.

3. Hade:

It is the complement angle of dip, i.e., the angle which the fault plane makes with the vertical plane or (90°-Dip -Hade).

4. Throw and heave:

The throw of a fault is the vertical component of the apparent displacement of abed, measured along direction of dip of the fault.

The heave of a fault, in a like manner, is the horizontal component of the apparent displacement. It is also known as gape.

5. Stratigraphic throw:

If the same bed occurs twice because of faulting, the perpendicular distance between them measured along a vertical section at right angles to the strike of the fault, is known, as stratigraphic throw.

6. Net-slip:

The total displacement due to a fault is des­cribed as its net-slip.