What is the Difference Between Normal Fault and Reverse Fault

The main difference between normal fault and reverse fault is that normal fault describes the downward movement of one side of the fault with respect to the other side whereas reverse fault refers to the upward movement of one side of the fault with respect to the other side.

In geology, a fault refers to a planar fracture or discontinuity that occurs as a result of rock-mass movement. Plate tectonic movements cause large fractures. E.g. transform faults. The release of energy that is associated with a fault is called an earthquake. There are different types of geological faults such as strike-slip fault, dip-slip fault, etc. Normal and reverse faults are the two major types of dip-slip fault.

Key Areas Covered

1. What is a Normal Fault 
     – Definition, Features, Formation
2. What is a Reverse Fault
     – Definition, Features, Formation
3. What is the Difference Between Normal Fault and Reverse Fault
     – Comparison of Key Differences

Key Terms

Fault, Normal Fault, Reverse Fault

What is Normal Fault

A normal fault is a type of dip-slip fault where one side of land moves downward while the other side stays still. The non-moving land is called the footwall. Moving wall is called the hanging wall. Moreover, the fault surface between footwall and hanging wall dips steeply. This steep changes from 50 to 90 degrees.

Figure 1: A Normal Fault

Garben and horst are two types of topographies related to a normal fault. A garben forms when a downthrown block is created between two normal faults dipping towards each other. A horst forms when a downthrown block is created between two normal faults dipping away from each other. Therefore, garben and horst topographies form due to processes that are opposite to each other.

What is a Reverse Fault

A reverse fault is a type of dip-slip fault where one side of the land moves upwards while the other side stays still. The non-moving land is called the footwall. Moving wall is called the hanging wall. Therefore, it is the opposite of a normal fault. This type of faults causes the compressive shortening of the crust. When compared to a normal fault, the dip of this type of fault is very steep (about 45 degrees). However, this type of faults is less common than normal faults.

Compressional stresses can cause a reverse fault. Here, the hanging wall and the footwall are pushed towards each other, causing a compression. In contrast, the normal fault is caused by the tensional stresses which cause the hanging wall and footwall to be pulled apart from each other.

Difference Between Normal Fault and Reverse Fault

Definition

A normal fault is a type of dip-slip fault where one side of land moves downward while the other side stays still. In contrast, a reverse fault is a type of dip-slip fault where one side of the land moves upwards while the other side stays still.

Formation

Normal faults form due to tensional stress, whereas reverse fault form due to compressive stress.

Mechanism

In normal faults, the hanging wall is pulled apart from the footwall; however, in reverse fault, the hanging wall is pushed towards the footwall.

Appearance

Moreover, in normal faults, there is a downward movement of one side of the fault with respect to the other side; however, in a reverse fault, there is an upward movement of one side of the fault with respect to the other side.

Conclusion

A fault refers to a planar fracture or discontinuity which occurs as a result of rock-mass movement. Normal fault and reverse fault are two types of fault in geology. The main difference between normal fault and reverse fault is that normal fault describes the downward movement of one side of the fault with respect to the other side whereas reverse fault refers to the upward movement of one side of the fault with respect to the other side.

Reference:

1. “Normal Fault.” Geology Page, 15 Sept. 2016, Available here.
2. “Normal Fault.” STUDY.COM, Available here.
3. “Fault (Geology).” Wikipedia, Wikimedia Foundation, 21 May 2020, Available here.
4. “What Is Reverse Fault.” STUDY.COM, Available here.

Image Courtesy:

1. “Normal-slip fault” By Bgwhite – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Faults6” By Actualist – Own work (CC BY-SA 3.0) via Commons Wikimedia