Which condition enhances the risk of liquefaction during seismic events?

The risk of liquefaction during seismic events is significantly enhanced by ground motion. Liquefaction occurs when saturated soil substantially loses strength and stiffness in response to applied stress, such as seismic shaking. During an earthquake, the intense ground motion can increase pore water pressures within the soil, reducing effective stress and thereby causing the soil to behave like a liquid.

When ground motion occurs, the vibrations create rapid, cyclic loading conditions that can exceed the soil's ability to withstand such forces, particularly in loose, saturated cohesionless soils, leading to the phenomenon of liquefaction. This is particularly critical in areas where the soil is water-saturated and has a significant potential for liquefaction under seismic conditions.

Other conditions like the water table being low, soil having high shear strength, or being dry can mitigate the risk of liquefaction. A low water table indicates drier conditions that reduce the likelihood of significant pore water pressure build-up. High shear strength in soil can also provide greater resistance to failure under seismic loading, while dry soil conditions do not have the necessary water content to facilitate liquefaction. Thus, ground motion stands out as the primary condition that can trigger this geotechnical issue during seismic activity.