Earthquake Faults—3 basic types...in brief (educational)

Summary

The video explains three types of faults in geology: normal, reverse, and strike-slip. A normal fault occurs when the hanging wall moves down relative to the footwall due to tensional forces, leading to extension. In contrast, a reverse fault sees the hanging wall moving up relative to the footwall, resulting from compressional forces and causing overall shortening. The strike-slip fault, characterized by a near-vertical fracture, involves horizontal movement of blocks on either side. If a block shifts left, it's a left lateral fault; if right, it's a right lateral fault. This concise overview highlights the fundamental mechanics of geological faulting.

Takeaways

• 😀 A normal fault occurs when the hanging wall moves down relative to the footwall due to tensional forces.
• 😀 Normal faults result in the extension of the Earth's crust.
• 😀 In a reverse fault, the hanging wall moves up relative to the footwall caused by compressional forces.
• 😀 Reverse faults lead to the overall shortening of the crust.
• 😀 A strike-slip fault is characterized by a near-vertical fracture where ground shifts horizontally.
• 😀 Horizontal shearing forces are responsible for the movement in strike-slip faults.
• 😀 If the block opposite to you shifts to the left when standing on one side of a strike-slip fault, it is classified as a left lateral fault.
• 😀 Conversely, if it moves to the right, it is called a right lateral fault.
• 😀 The types of faults discussed include normal faults, reverse faults, and strike-slip faults.
• 😀 Each type of fault is associated with specific geological forces and movements.

Q & A

What is a normal fault?

A normal fault is a type of fault where the block above the fault, called the hanging wall, moves downward relative to the block below the fault, called the footwall. This motion occurs due to tensional forces, resulting in extension of the crust.

What causes motion in a reverse fault?

In a reverse fault, the hanging wall moves upward relative to the footwall. This motion is caused by compressional forces, which result in overall shortening of the crust.

How do tensional forces influence fault movement?

Tensional forces cause the hanging wall of a normal fault to move downward, leading to extension of the crust and an increase in the distance between geological features.

What is the result of compressional forces on a fault?

Compressional forces cause the hanging wall of a reverse fault to move upward, which results in the shortening of the crust and the convergence of geological features.

What defines a strike-slip fault?

A strike-slip fault is a near-vertical fracture where the ground shifts horizontally due to shearing forces. The motion along the fault occurs parallel to the surface.

What happens in a left lateral strike-slip fault?

In a left lateral strike-slip fault, when standing on one side of the fault, the block on the opposite side shifts to the left. This type of fault is caused by horizontal shearing forces.

What distinguishes a right lateral strike-slip fault?

In a right lateral strike-slip fault, when standing on one side of the fault, the block on the opposite side shifts to the right. This is also caused by horizontal shearing forces.

What are the three main types of faults discussed in the transcript?

The three main types of faults discussed are normal faults, reverse faults, and strike-slip faults.

What role do shearing forces play in fault movement?

Shearing forces, which are horizontal forces, cause the ground to shift parallel to the surface, resulting in strike-slip faults where the displacement occurs horizontally along the fault line.

How does a reverse fault differ from a normal fault in terms of crust movement?

In a reverse fault, the hanging wall moves upward relative to the footwall, leading to crustal shortening, while in a normal fault, the hanging wall moves downward, leading to crustal extension.