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Liquefaction and Sea-Level Rise

February 7, 2022

U.S. Geological Survey scientists studied the impacts of sea-level rise on liquefaction severity around the San Francisco Bay Area, California for the magnitude 7.0 ‘HayWired’ earthquake scenario along the Hayward Fault. This work emerged from stakeholder engagement for the releases of the USGS ‘HayWired’ earthquake scenario and the Coastal Storm Modeling System projects, in which local planners and engineers asked where, why, and by how much liquefaction hazards may change due to sea-level rise in the future. A team of geologists and hydrologists assessed the impacts of sea-level rise on liquefaction by computing changes in liquefaction potential index for 347 boring sites around the San Francisco Bay for groundwater table models developed for current and increased sea-levels of up to 5 meters for the magnitude 7.0 ‘HayWired’ earthquake scenario. This study describes the behavior of San Francisco Bay area soils and identifies characteristics of potentially sensitive sites of concern. 

The sensitive sites are artificial fill around the Bay Area margins where the water table is already shallow. For the HayWired scenario ground shaking, these sites may already have a severe liquefaction hazard, and with 1 meter of sea-level rise, the hazard at more of these sites increases to severe. The liquefaction intensity for the HayWired scenario shaking for some natural soil sites may change from low to moderate-high with higher levels of sea-level rise.

A picture of a damaged road caused by lateral spread liquefaction
Lateral spread caused by liquefaction during the Loma Prieta earthquake, 1989