ASBOG Practice Exam

When observing a fault, what is the hanging wall?

1. The surface below the fault line

2. The surface above the fault line

3. The surface at the fault line

4. The surface adjacent to the fault

The correct answer is: The surface above the fault line

The hanging wall refers to the block of rock that lies above a fault plane. In the context of a fault, understanding the orientation is crucial for geological interpretation. When you look at a fault, if you were to stand on the footwall—the block that is below the fault—you would be looking up at the hanging wall, which is the rock mass that has moved upward relative to the footwall during faulting. This terminology is essential in structural geology, as it helps describe the relationship and movement between the two fault blocks. Grasping this concept is critical for analyzing geological formations and understanding the mechanics of fault movement, as well as related phenomena such as earthquakes and rock mechanics. The surface below the fault line would be identified as the footwall, while the surface at the fault line relates to the fault itself rather than the hanging wall. Therefore, recognizing the hanging wall as the block above the fault distinguishes it from other aspects of the fault.