Item 26 - Updated Hazard Mitigation Plan

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Hazard Mitigation Plan | 2022 Earthquake Hazards - 67 - Liquefaction Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other events. Liquefaction occurs in saturated soils, which are soils in which the space between individual soil particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. Because liquefaction only occurs in saturated soil, its effects are most commonly observed in low lying areas. Typically, liquefaction is associated with shallow groundwater, which is less than 50 feet beneath the earth’s surface. Map: Liquefaction Zones shows the City’s significant susceptibility to liquefaction. Map: Liquefaction Zones (Source: Department of Conservation)