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625 Cypress Avenue Geotechnical Investigation Project No. W1895-88-01 - 4 - April 23, 2024 construction may be actually higher than those encountered during our investigation. In addition, recent requirements for storm water infiltration could result in shallower seepage conditions in the region. Proper surface drainage of irrigation and precipitation will be critical for future performance of the project. Recommendations for drainage are provided in the Surface Drainage section of this report (see Section 7.13). 6. GEOLOGIC HAZARDS 6.1 Surface Fault Rupture The numerous faults in Southern California include Holocene-active, pre-Holocene, and inactive faults. The criteria for these major groups are based on criteria developed by the California Geological Survey (CGS, formerly known as CDMG) for the Alquist-Priolo Earthquake Fault Zone Program (CGS, 2018). By definition, a Holocene-active fault is one that has had surface displacement within Holocene time (about the last 11,700 years). A pre-Holocene fault has demonstrated surface displacement during Quaternary time (approximately the last 1.6 million years) but has had no known Holocene movement. Faults that have not moved in the last 1.6 million years are considered inactive. The site is not within a state-designated Alquist-Priolo Earthquake Fault Zone (CGS, 2024a; 2024b) for surface fault rupture hazards. No Holocene-active or pre-Holocene faults with the potential for surface fault rupture are known to pass directly beneath the site. Therefore, the potential for surface rupture due to faulting occurring beneath the site during the design life of the proposed development is considered low. However, the site is located in the seismically active Southern California region, and could be subjected to moderate to strong ground shaking in the event of an earthquake on one of the many active Southern California faults. The faults in the vicinity of the site are shown in Figure 4, Regional Fault Map. The closest trace of a Holocene-active fault to the site is the Newport-Inglewood Fault Zone located approximately 8.6 miles to the southwest (Ziony and Jones, 1989). Other nearby active faults are the Whittier Fault, the Glen Ivy section of the Elsinore Fault, and the Chino Fault located approximately 12½ miles north, 15½ miles northeast, and 16½ miles northeast of the site, respectively (Ziony and Jones, 1989). The active San Andreas Fault Zone is located approximately 43 miles northeast of the site. Several buried thrust faults, commonly referred to as blind thrusts, underlie the Los Angeles Basin (including the Orange County Coastal Plain) at depth. These faults are not exposed at the ground surface and are typically identified at depths greater than 3.0 kilometers. The October 1, 1987, Mw 5.9 Whittier Narrows earthquake and the January 17, 1994, Mw 6.7 Northridge earthquake were a result