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625 Cypress Avenue <br />Geotechnical Investigation <br /> <br />Project No. W1895-88-01 - 10 - April 23, 2024 <br />ASCE 7-16 SITE-SPECIFIC PEAK GROUND ACCELERATION <br />Parameter Value ASCE 7-16 Reference <br />Site-Specific MCEG <br />PGAM 0.651g Section 21.5 <br /> <br />6.3.6 Deaggregated Seismic Source Parameters <br />Deaggregation of the MCE peak ground acceleration was performed using the USGS online Unified <br />Hazard Tool, 2014 Conterminous U.S. Dynamic edition (v4.2.0). The result of the deaggregation analysis <br />indicates that the predominant earthquake contributing to the MCE peak ground acceleration is <br />characterized as a 7.3 magnitude event occurring at a hypocentral distance of 12.72 kilometers from <br />the site. <br />Deaggregation was also performed for the Design Earthquake (DE) peak ground acceleration, and the <br />result of the analysis indicates that the predominant earthquake contributing to the DE peak ground <br />acceleration is characterized as a 6.47 magnitude occurring at a hypocentral distance of 26.94 <br />kilometers from the site. <br />Conformance to the criteria in the above tables for seismic design does not constitute any kind of <br />guarantee or assurance that significant structural damage or ground failure will not occur if a large <br />earthquake occurs. The primary goal of seismic design is to protect life, not to avoid all damage, since <br />such design may be economically prohibitive. <br />6.4 Liquefaction Potential <br />Liquefaction is a phenomenon in which loose, saturated, relatively cohesionless soil deposits lose shear <br />strength during strong ground motions. Primary factors controlling liquefaction include intensity and <br />duration of ground motion, gradation characteristics of the subsurface soils, in-situ stress conditions, <br />and the depth to groundwater. Liquefaction is typified by a loss of shear strength in the liquefied layers <br />due to rapid increases in pore water pressure generated by earthquake accelerations. <br />The current standard of practice, as outlined in the “Recommended Procedures for Implementation of <br />DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction in California” and <br />“Special Publication 117A, Guidelines for Evaluating and Mitigating Seismic Hazards in California” <br />requires liquefaction analysis to a depth of 50 feet below the lowest portion of the proposed structure. <br />Liquefaction typically occurs in areas where the soils below the water table are composed of poorly <br />consolidated, fine- to medium-grained, primarily sandy soil. In addition to the requisite soil conditions,