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Caribou Industries Proposed Alternative Seismic Improvements - 888 North Main Street July 25, 2018 Page 4 Slope Stability The relatively flat-lying topography at the site precludes both stability problems and the potential for lurching (earth movement at right angles to a cliff or steep slope during ground shaking). There are no known landslides near the site, nor is the site in the path of any known or potential landslides (CGS, 2018c). Additionally, the site is not within an area identified as having a potential for earthquake-induced landslides (CDMG, 1998). Tsunamis, Inundation, Seiches, Flooding and Subsidence The site is not in a coastal area and at an approximate mean elevation of 128 feet AMSL. Therefore, tsunamis (seismic sea waves) are not considered a hazard at the site. According to the County of Orange Safety Element (2012), the site is not located downslope of any other large bodies of water that could adversely affect the site in the event of earthquake-induced dam failures or seiches (wave oscillations in an enclosed or semi-enclosed body of water). Therefore, the potential for inundation at the site as a result of an earthquake-induced dam failure is considered low. The site is located outside the 0.2% annual chance floodplain, Zone X, as defined by the Federal Emergency Management Association (FEMA, 2009). Therefore, the potential for flooding to affect the site is considered low. The site is not within an area of known subsidence associated with fluid withdrawal (groundwater or petroleum), peat oxidation, or hydrocompaction (City of Santa Ana, 2010). Oil Wells and Methane Gas The site is not located within the limits of an oil field according to the California Division of Gas and Geothermal Resources' Well Finder System (DOGGR, 2018). The closest known oil exploration wells are over one mile to the northeast and southwest of the site. Per DOGGR, the wells are classified as a "plugged." Although considered a remote possibility, abandoned wells or other undocumented wells could be encountered if excavations are performed. Any wells encountered should be abandoned in accordance with current DOGGR standards and regulations. Geologic Conclusions Based on the available geologic data, active or potentially active faults with the potential for surface fault rupture are not known to be located directly beneath or projecting toward the site. Therefore, the potential for surface rupture due to fault plane displacement propagating to the surface at the site during the design life of the proposed building is considered low. The site could be subjected to strong ground shaking in the event of an earthquake due to the close proximity to active faults. This hazard is common in Southern California and the effects of ground shaking can be mitigated by proper engineering design and construction in conformance with current building codes and engineering practices. The relatively flat-lying topography at the site precludes both stability problems and the potential for lurching (earth movement at right angles to a cliff or steep slope during ground shaking). The potential for other geologic hazards such as liquefaction, tsunamis, inundation, seiches, flooding, and subsidence affecting the site is also considered low. 3.0 Development of Site-Specific Response Spectra We have performed a Probabilistic Seismic Hazard Analysis (PSHA) using the computer program OpenSHA (Field et al. 2003) and a Deterministic Seismic Hazard Analysis (DSHA) using the computer program EZ-FRISK (Risk Engineering, 2015) in order to develop site-specific response spectra (RS) in accordance with the 2016 California ...