Can Earthquakes Cause Structural Damage Without Shaking?

Seismic Soil Liquefaction

Liquefaction occurs when water-saturated soil loses strength during an earthquake, causing it to behave like a liquid. This can lead to structural damage, even if the soil itself doesn’t experience significant shaking. Liquefaction can cause foundations to sink or shift, compromising the stability of buildings. In areas with loose or water-saturated soil, liquefaction is a significant concern, particularly during earthquakes with shallow epicenters. For example, during the 1964 Alaska earthquake, liquefaction caused significant damage to buildings and infrastructure in the coastal areas.

Soil Settlement and Ground Settlement

Soil settlement and ground settlement occur when the ground itself shifts or settles, often due to the weight of nearby structures. This can be exacerbated by earthquakes, which can cause the ground to compact or shift. Buildings on loose or unstable soil may experience structural damage or collapse due to soil settlement. For example, during the 1989 Loma Prieta earthquake in California, soil settlement caused significant damage to buildings and roads in the Santa Cruz Mountains.

Identifying and Mitigating the Risk

To identify the risk of seismic soil liquefaction, soil settlement, and ground settlement, it’s essential to conduct thorough site investigations and geotechnical assessments before building construction. This can include soil borings, laboratory testing, and field observations to determine the site’s liquefaction potential, soil properties, and settlement behavior. In areas with high liquefaction potential, engineers can use techniques such as soil densification, deep foundations, or other seismic-resistant design methods to mitigate the risk of structural damage.