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SCE Santa Ana October 25,2019 Project No. 3.31634 Page 6 9.2 Soil Lurching Soil lurching refers to the rolling motion on the ground surface by the passage of seismic surface waves. Effects of this nature are likely to be most severe where the thickness of soft sediments varies appreciably under structures. In its present condition, the potential for lurching at the subject site is considered low due to the overall relative density of site soils. 9.3 Liquefaction and Dynamic Settlement The project site is located within the Tustin Liquefaction Hazard Zone (Seismic Hazard Zone Report for the Tustin 7.5-Minute Quadrangle, Orange County, California, CGS, 2001). Liquefaction is characterized by a loss of shear strength in the affected soil layers, thereby causing the soil to behave as a viscous liquid. This effect may be manifested at the ground surface by settlement, sand boils, and bearing capacity failure below structures. Dynamic settlement in dry sands can occur due to densification of the sand as a result of vibration stemming from the seismic event. In order for the potential effects of liquefaction to be manifested at the ground surface, the soils generally have to be granular, loose to medium-dense and saturated relatively near the ground surface (≤ 40-feet) and must be subjected to ground shaking of a sufficient magnitude and duration. The potential for liquefaction to occur is considered very low, given the lack of a static or perched water table (See Section 6.2) and the nature of soils on-site, predominantly clay and silt. Because the liquefaction potential is considered very low, the potential for ground failures associated with liquefaction, i.e post liquefaction reconsolidation, and sand boils are also considered very low. 9.6 Lateral Spreading Lateral spreading is a type of liquefaction induced ground failure that forms on gentle slopes as a result of seismic activity and has a fluid like movement. It differs from slope failure in that complete ground failure involving large movement does not occur due to the relatively smaller gradient of the initial ground surface. Due to the site being relatively level and the lack of an adjacent free face to drive lateral spreading, the potential for lateral spreading is considered very low. 51 of 100 1327 S Grand Ave 12/12/2024