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Eugene -Springfield Area Natural Hazards Mitigation Plan <br />2. Hazard Descriptions <br />Subduction Zone (CSZ) or combined crustal events.16 Given the potential for <br />damage and the probability of a CSZ occurrence, Eugene and Springfield are <br />primarily focused on a potential CSZ incident for earthquake mitigation planning <br />purposes. <br />2.3.1 Causes and Characteristics of the Hazard <br />Seismic incidents were once thought to pose little or no threat to Oregon <br />communities. However, recent earthquakes and scientific evidence indicate the risk <br />to people and property is much greater than previously considered. Oregon, and the <br />Pacific Northwest in general, are susceptible to earthquakes from four sources: <br />1. The offshore Cascadia Subduction Zone; <br />2. Deep intraplate incidents within the subducting Juan de Fuca Plate; <br />3. Earthquakes associated with renewed volcanic activity; and <br />4. Shallow crustal incidents within the North American Plate. <br />An earthquake could impact the entire Eugene -Springfield metro area as well as <br />surrounding areas. The specific hazards associated with an earthquake include: <br />Ground Shaking <br />Ground shaking is defined as the motion of seismic waves felt on the Earth's surface <br />caused by an earthquake. Ground shaking is the primary cause of earthquake <br />damage. <br />Ground Shaking Amplification <br />Ground shaking amplification refers to how soils and soft sedimentary rocks, located <br />near the surface, affect ground shaking from an earthquake. They can increase or <br />decrease the amplification as well as the frequency of the shaking. <br />Surface Faulting <br />Surface faulting occurs when displacement reaches the earth's surface during a <br />movement along a fault. Such faulting can result from movement deep within the <br />earth or at the surface. <br />Earthquakes occurring from deep -lying faults usually create only ground shaking. <br />18 United States. Salem, OR. Oregon Military Department Office of Emergency Management. <br />Oregon Natural Hazards Mitigation Plan. 2015. Accessed October 2017. <br />httl)s://www.oregon.gov/LCD/NH/Documents/Approved 2015ORNHMp.pdf <br />2-6 January 2020 <br />