Resolution No. 5303 - Laserfiche WebLink

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Eugene -Springfield Area Natural Hazards Mitigation Plan 2. Hazard Descriptions Earthquake -Induced Landslides Landslides occur due to the shaking motion of an earthquake destabilizing the ground. Areas already prone to landslides have a much higher risk of an incident occurring during an earthquake. Liquefaction Liquefaction is a process by which water -saturated sediment temporarily loses strength and acts as a fluid instead of a solid. As the sediment loses strength, it also loses the ability to support weight. This effect can be caused by ground shaking. Severity The severity of an earthquake is dependent upon several factors including the distance from the earthquake's source (epicenter,) the ability of the soil and rock to conduct seismic energy, the degree (i.e. angle) of slope, the composition of slope, the magnitude of the earthquake, and the type of earthquake. Maps showing the location of various earthquake related hazards are in Section 3. 2.3.2 Climate Change At this point, it is unknown how climate change may affect how an earthquake impacts Eugene and Springfield. Changing soil conditions, due to climate change, could affect how earthquakes propagate throughout the area, but the extent or effect of this factor is unknown at this time. 2.3.3 History of the Hazard in Eugene -Springfield Historically, earthquakes of sufficient intensity to cause significant damage in the Mid/Southern Willamette Valley region have occurred as offshore Cascadia Subduction Zone (CSZ) earthquakes of magnitudes of around 8 to 9. Approximate years of significant CSZ incidents are: • 1400 BCE • 1050 BCE • 600 BCE • 400 CE • 750 CE • 900 CE • 1700 CE 2-7 January 2020