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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br />Table 4-50. Modified Mercalli Scale vs. Richter Scale <br />Earthquakes can trigger other types of ground failures, which could contribute to the damage. These <br />include flow failures, landslides, and liquefaction. Liquefaction is not a type of ground failure; however, it <br />is a physical process that occurs when shaking can mix groundwater and soil, liquefying and weakening <br />the ground that supports buildings and severing utility lines. This is a problem in floodplains where the <br />water table is relatively high, and the soil is more susceptible to liquefaction. l3a <br />The National Earthquake Hazards Reduction Program (NEHRP) defined six (6) different site <br />classifications, based on the type of soil and rock in the area, and their shear-wave velocity. NEHRP soil <br />type A (hard rock), B (rock), and C (very dense soil and soft rock) typically can sustain low magnitude <br />ground shaking without much effect. On the other hand, NEHRP soil types D (stiff soil), E (soft clay soil), <br />and F (could contain different types of soils, requiring site-specific evaluations) are most affected by <br />ground shaking making these areas more susceptible to liquefaction.-135 Figure 4-12 shows the NEHRP <br />soil classifications present in Kittitas County. <br />134 United States Geological Survey. (n.d.). What are the Effects of Earthquakes? Retrieved from <br />ake-haza rds/what-are-effects- <br />135 Nolan, J. (2022). The Effects of SoilType on Earthquake Damage. Retrieved from <br />wsrb.com/blo cts-of-soil- <br />Not felt 1-2L lnstrumental <br />3ll. Just Perceptible Felt by only a few people, especially on upper floors of tall buildings <br />3.5lll. Slight Felt by people lying down, seated on a hard surface, or in the upper <br />stories of tall buildings. <br />4lV. Perceptible Felt indoors by many, by few outside; dishes and windows rattle. <br />V. Rather Strong €ener'ally fb,l{' by: evonyonel sleepfuig Feopfe may be awa Kened. <br />5Vl. Strong Trees sway, chandeliers swing, bells ring, some damage from falling <br />object. <br />5.5Vll. Very Strong General alarm; walls and plaster crack. <br />6Vlll. Destructive Felt in moving vehicles; chimneys collapse; poorly constructed buildings <br />seriously damaged. <br />Obvious ground cracks; railroad tracks bent; some landslides on steep <br />r Few buildings survive; bridges damaged or destroyed; all services <br />interrupted (electrical, water, sewage, railroad; severe landslides). <br />Total destruction; objects thrown into the air; river courses and <br />lntensity Effects <br />7.5 <br />B <br />7 <br />altered <br />hillsides. <br />Richter <br />Scale <br />l)(, ilttiit,rti; <br />X. Disastrous <br />Xl. Very Disastrous <br />Xll. Catastrophic <br />Chapter 4: Hazard ldentification and Risk Assessment 110