Fault and its types

In geology, fault is a structure developed due to the slip- off of the rocks from its original position.

The displacement of the rocks is due to tensional movement caused by endogenetic force.

During the displacement of the rocks from its original position, a plane is formed known as fault plane.

The plane along which the blocks are displaced is called fault plane.

Fault plane divides the block into two different parts, i.e footwall and hanging wall.

The block above the fault plane is called hanging wall and below it is footwall.

MECHANISM OF FAULTING

Rocks are considered as elastic body as they can resist some amount of stress applied.

Within the elastic limit of the rocks, they can resist the stress without being deformed.

The stress/force mentioned here is tensional stress which is caused due to endogenetic activities.

But when the stress applied on the rock exceed its elastic limit, fracture is developed within the rocks.

And at the maximum level of stress, fractured block cannot resist more stress and slip off suddenly from its original position.

The fractured block displaces along a plane called fault plane and developing a geological structure called fault.

It is important to know, that fault is only formed when the fractured block displaces its original position along the plane.

The sudden slip–off of the rock releases he energy stored in the rock in the form of waves.

These waves are called seismic waves which are responsible causing the earthquake.

This concludes that, tectonic earthquake is the result of the fault.

TYPES OF FAULT

1) Normal fault:

This geological structure is formed when the hanging wall moves relatively downward to the footwall.

2) Reverse fault:

This fault is formed when the hanging wall moves relatively upwards to footwall.

3) Strike slip fault:

It is also called transcurrent fault.

This fault is formed when two blocks moves laterally side pass each other.

It is also called left lateral or right lateral depending upon their movement along the strike.

4) Oblique slip fault:

This fault is formed when two blocks move obliquely pass each other.

This can also occur due to the slip-off of strike slip fault.

4) Thrust Fault:

As when the hanging wall moves relatively over the footwall, then it is termed as reverse fault.

as the dip of the such fault might exceed more than angle of 45.

But in case of the thrust fault it's same for the movement of the hanging wall but the angle of dip is low.

This means, the low angle reverse fault is termed as the thrust fault.

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FOLDS

references

. Billings, Marland Pratt. Structural Geology,3rd Edition , (1972).

Brodie, Kate; Fettes, Douglas; Harte, Ben; Schmid, Rolf (29 January 2007), Structural terms including fault rock terms, International Union of Geological Sciences

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