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The Mark at Eugene January 6, 2026 Seismic Hazard Study 11 Project No.: 2251077 Eugene, Oregon Landmark Construction, LLC Based on the presence of limited fill and alluvial soil followed by very stiff residual soil and the results of the ReMi study, it is our opinion the amplification hazard is low to moderate and is consistent with an OSSC/IBC Site Class D soil profile (stiff soil, 700 to 1,000 ft/s). The DOGAMI hazard studies indicate the amplification susceptibility for the site is low (NEHRP Site Class B) (Black et al., 2000; Burns et al., 2008). The site is expected to experience strong ground shaking during a CSZ earthquake due to its proximity to the CSZ (DOGAMI, 2018). See the main report for more discussion on the site response. SEISMIC DESIGN Design Earthquakes The 2022 OSSC, Section 1803.3.2.1, requires the design of structures classified as essential or hazardous facilities and of major and special occupancy structures to address, at a minimum, the following earthquakes: Crustal: A shallow crustal earthquake on a real or assumed fault near the site with a minimum MW 6.0 or the design earthquake ground motion acceleration determined in accordance with the OSSC 2022 Section 1613. Intraplate: A deep CSZ intraplate earthquake with a MW greater than 7.0. Interface: A CSZ interface earthquake with a MW of at least 8.5. The design maximum considered earthquake ground motion maps provided in the 2022 OSSC, are based on modified (risk-targeted) 2014 maps prepared by the USGS for an earthquake with a 2% probability of exceedance in 50 years (i.e., a ±2,475-year return period) for design spectral accelerations (USGS, 2014b). The modifications include factors to adjust the spectral accelerations to account for directivity and risk. The 2014 USGS maps were established based on probabilistic studies and include aggregate hazards from a variety of seismic sources. The USGS interactive deaggregation for a 2,475-year return period indicates the seismic hazard at the site is dominated by the CSZ. Crustal earthquakes were included in the studies but were not considered to be a principal seismic hazard at this site. Seismic sources representing at least 4.5% of the overall hazard are summarized in Table 4D. The earthquake magnitudes and source-to-site distances used to generate the 2014 USGS maps satisfy the requirements of 2022 OSSC. Seismic design parameters are discussed in the Site Response section of the main report, and the design response spectra are shown in Figure 3A (Appendix A).