What is the phenomenon called when unsupported cliffs or stream banks move toward a free face during an earthquake?

The phenomenon of unsupported cliffs or stream banks moving toward a free face during an earthquake is known as ground lurching. This occurs when the ground shakes and destabilizes, causing materials that were previously stable to lose their support and shift. The seismic activity leads to a sudden redistribution of stress on the slopes, which may result in the movement of rocks and soil toward an unsupported edge.

Ground lurching is significant in understanding geohazards associated with earthquakes, especially in areas with steep topography. It can lead to landslides, rockfalls, and other forms of mass wasting, posing risks to infrastructure and ecosystems in the vicinity.

In contrast to this, flow typically refers to the movement of materials like mud or debris in a fluid-like manner, which may happen during or after an earthquake but is not specifically tied to the movement of cliffs toward a free face. Holocene fault refers to faults that have active movement in the current geological epoch, while fault-line scarp is a feature formed by vertical displacement along a fault line rather than the lateral motion observed during ground lurching.