The Mark at Eugene January 6, 2026 <br />Seismic Hazard Study 6 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />Table 1 D. USGS Class A and Class B Crustal Faults <br />within a ±50-mile Radius of the building (1) <br />Fault Name and <br />Class <br />Fault <br />Number <br />Approximate <br />Length <br />(miles) <br />Approximate <br />Distance and <br />Direction from Site <br />(miles) (2) <br />Last Known <br />Deformation <br />(years) (3) <br />Slip Rate <br />(mm/yr) <br />Upper Willamette <br />River (B) 863 ±27 ±25 SE <1.6 million <0.20 <br />Owl Creek (A) 870 ±9 ±30 N-NW <750,000 <0.20 <br />Corvallis (B) 869 ±25 ±36 NW <1.6 million <0.20 <br />Unnamed faults <br />near Sutherlin (B) 862 ±17 ±41 SW and-SE <750,000 <0.20 <br />Unnamed Siuslaw <br />River anticline (A) 887 ±8 ±43 W <750,000 0.2 and <br />1.0 <br />Salem-Eola Hills <br />homocline (A) 719 ±20 ±49 N-NE <1.6 million <0.20 <br />(1) Fault data based on Personius et al., 2003 and USGS, 2014a, 2016 and 2022. <br />(2) Distance and direction from site to nearest surface projection of the fault. <br />There is much debate and uncertainty regarding the size, rupture type, and frequency <br />of CSZ earthquakes. Numerous detailed studies of coastal subsidence, tsunami, and <br />turbidite deposits estimate a wide range of CSZ earthquake recurrence intervals. <br />Turbidite deposits in the Cascadia Basin have been investigated to help develop a <br />paleoseismic record for the CSZ and estimate recurrence intervals for interface <br />earthquakes (Adams, 1990; Goldfinger et al., 2012). <br />A study of offshore turbidites from the last ±10,000 years suggests the return period <br />for interface earthquakes varies with location and rupture length. That study estimated <br />an average recurrence interval of ±220 to 380 years for an interface earthquake on <br />the southern portion of the CSZ, and an average recurrence interval of ±500 to <br />530 years for an interface earthquake extending the entire length of the CSZ <br />(Goldfinger et al., 2012). Older, deep-sea cores have been re-examined more recently, <br />and the findings may indicate greater Holocene stratigraphy variability along the <br />Washington coast (Atwater et al., 2014). Additional research by Goldfinger for <br />the northern portion of the CSZ suggests a recurrence interval of ±340 years for the <br />northern Oregon Coast (Goldfinger et al., 2016). The most recent CSZ interface <br />earthquake occurred ±325 years ago (January 26, 1700) (Nelson et al., 1995; Satake <br />et al., 1996).