Question

If, during an earthquake, a hanging wall slides upward relative to a footwall, the fault is called ___________ if the fault plane is steep (closer to vertical than horizontal)

Answer 1

In an earthquake where the hanging wall slides upward relative to the footwall on a steep fault plane, the fault is called a reverse fault. If the fault is less steep, it would be considered a thrust fault.

Step-by-step explanation:

When an earthquake results in a hanging wall sliding upward relative to a footwall and the fault plane is steep, closer to vertical than horizontal, the fault is called a reverse fault. Reverse faults are formed during times of compression and the shortening of the Earth's crust. While normal faults occur with the hanging wall moving down due to extension, reverse faults involve the hanging wall moving upwards. On the other hand, if the fault has a shallow dip, less than 30°, it is known as a thrust fault, with the moving block called the allochthonous block thrusting over the autochthonous block. Occasionally, erosion may isolate parts of the allochthonous block as a klippe, or expose the autochthonous material in a window.