What process describes the movement of a fractured mass laterally, often along a basal shear surface?

The movement of a fractured mass laterally along a basal shear surface is best described by the term "Lateral Spread." This process occurs when a destabilized mass of soil or rock on a slope or in an area of low gradient begins to move horizontally. Typically, this can happen during seismic shaking or under certain loading conditions, where the shear resistance of the material is overcome, allowing it to slide or spread outwards.

In scenarios where lateral spreading takes place, it is essential to consider the underlying layers, as these often play a crucial role in providing the shear surface along which the movement occurs. Factors such as soil composition, moisture content, and the presence of fissures can all contribute to the likelihood of lateral spread events, particularly in loose, saturated materials.

Understanding this process is critical in geological assessments, especially in areas prone to earthquakes or landslides, as it can lead to significant structural damage and changes in the topography. The other terms, while related to soil and materials movement, describe different processes: Liquefaction involves a solid material behaving like a liquid under stress, Hydrocompaction refers to the volume reduction of saturated sediments, and Microseism involves low-magnitude seismic events often unnoticed by humans.