1610 SE EVERETT MALL WAY Geotech Report 2022-10-25

Subsurface Exploration, Geologic Hazard, and Krebs Property Preliminary Geotechnical Engineering Report Everett, Washington Geologic Hazards and Mitigations II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and shallow ground water conditions as observed and discussed herein. 5.0 SEISMIC HAZARDS AND MITIGATION Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 2001, 6.8-magnitude event; and the 1965, 6.5-magnitude event. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 5.1 Surficial Ground Rupture The nearest known fault trace to the project site is the South Whidbey Island Fault, located within approximately 6 miles to the southwest. No surficial faulting or earth rupture associated with the South Whidbey Island Fault has been documented to date in the Snohomish County region. 5.2 Seismically Induced Landslides The risk of damage to the proposed project by seismically induced landsliding is low due to the lack of steep slopes in the project area. No mitigation of landslide hazards is warranted. 5.3 Liquefaction The encountered stratigraphy has a low potential for liquefaction due to its dense state and lack of adverse ground water conditions. No mitigation of liquefaction hazards is warranted. February 13, 2007 ASSOCIATED EARTH SCIENCES,INC. TJP/id-KE070023A1-Prof ects120070023IKEIWP Page 5