The Mark at Eugene January 6, 2026 <br />Seismic Hazard Study 1 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />SEISMIC HAZARD STUDY <br />THE MARK AT EUGENE <br />EUGENE, OREGON <br />INTRODUCTION <br />This seismic hazard study was completed to identify potential geologic and seismic <br />hazards and evaluate the effect those hazards may have on the proposed project. The <br />study fulfills the requirements presented in the 2022 Oregon Structural Specialty Code <br />(OSSC), Section 1803 for site-specific seismic hazard reports for major structures <br />(ORS 455.447) or Risk Category III or IV buildings, which include essential and <br />hazardous facilities and major and special occupancy structures (OSSC, 2022). <br />The following sections provide a discussion of the local and regional geology, seismic <br />and tectonic setting, earthquakes, and seismic hazards. A detailed discussion of the <br />subsurface conditions at the project location, including exploration logs, is provided in <br />the main report. Geologic time and age relations of soil and rock units referred to in this <br />document are based on the 1983 Geologic Time Scale unless otherwise noted (Palmer, <br />1983). <br />LITERATURE REVIEW <br />Available geologic and seismic publications and maps were reviewed to characterize <br />the local and regional geology and evaluate relative seismic hazards at the site. <br />Information from geotechnical and seismic hazard investigations previously conducted <br />by others and Foundation Engineering at the site and by Foundation Engineering in the <br />surrounding area were also reviewed. A nearby boring and shear wave velocity log, <br />which is part of a seismic hazard mapping project for the Eugene-Springfield area <br />completed by the Oregon Department of Geology and Mineral Industries (DOGAMI), <br />was also reviewed in addition to the current shear wave refraction microtremor <br />analysis (ReMi) study completed on site. <br />Regional Geology <br />Most of Oregon is geologically young, especially areas west of the Cascade Mountain <br />Range, which are less than 50 million years old. At the western margin of Oregon is <br />the Cascadia Subduction Zone (CSZ). The CSZ is a converging, oblique plate boundary <br />where the Juan de Fuca oceanic plate is being subducted beneath the western edge <br />of the North American continental plate (Geomatrix Consultants, 1995). The CSZ <br />extends from central Vancouver Island, in British Columbia, Canada, through <br />Washington and Oregon to Northern California in the United States (Atwater, 1970). <br />Much of the State is formed as a result of CSZ movement. Volcanism, earthquakes, <br />folding, faulting, creation of the volcanic arc, accumulation of marine sediments along <br />the ocean floor including exotic terranes west of the subduction zone (accretion), uplift <br />of oceanic and other sediments on the western margin of the North American plate, <br />and erosion of these rocks have all helped form Western Oregon.