The Mark at Eugene January 6, 2026 <br />Seismic Hazard Study 5 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />• Class A – Faults with geologic evidence supporting tectonic movement in the <br />Quaternary known or presumed to be associated with large-magnitude <br />earthquakes. <br />• Class B – Faults with geologic evidence that demonstrates the existence of a <br />fault or suggests Quaternary deformation, but either: 1) the fault might not <br />extend deep enough to be a potential source of significant earthquakes or 2) the <br />current evidence is too strong to confidently classify the fault as a Class C but <br />not strong enough to classify it as a Class A. <br />• Class C – Faults with insufficient evidence to demonstrate 1) the existence of a <br />tectonic fault, or 2) Quaternary movement or deformation associated with the <br />feature. <br />• Class D – Geologic evidence indicates the feature is not a tectonic fault or <br />feature. <br />Class A and B faults are included in the USGS fault database and interactive fault map. <br />USGS considers 17 features in Oregon to be Class C faults (Personius et al., 2003). <br />The Class C Harrisburg anticline is ±16 miles north-northwest of the site. The USGS <br />does not consider any features in Oregon as Class D (Personius et al., 2003). <br />A review of nearby faults was completed to evaluate the seismic setting and the <br />potential seismic sources. A few concealed and inferred crustal faults are located <br />within ±10 miles of the site; however, none of the nearby faults show any evidence <br />of movement in the last ±1.6 million years (Palmer, 1983; Geomatrix Consultants, <br />1995; Personius et al., 2003; USGS, 2016, 2022). <br />Six potentially active Quaternary Class A and B crustal fault zones have been mapped <br />by the USGS within ±50 miles of the site (Palmer, 1983; Geomatrix Consultants, <br />1995; Personius et al., 2003; USGS, 2014a, 2016, 2022). These faults are listed in <br />Table 1D. Figure 1D shows the approximate surface projection locations of these <br />faults. <br />Historic Earthquakes <br />CSZ Interface Earthquakes. No significant interface (subduction zone or megathrust) <br />earthquakes have occurred on the CSZ in historic times. However, several <br />large-magnitude (>M ~8.0, M = unspecified magnitude scale) subduction zone <br />earthquakes are thought to have occurred in the past few thousand years. This is <br />evidenced by tsunami inundation deposits, combined with evidence for episodic <br />subsidence along the Oregon and Washington coasts (Peterson et al., 1993; Atwater <br />et al., 1995).