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2015 IBC Parameter Recommended Values <br /> Short Period Spectral Acceleration,Ss(percent g) 119.7 <br /> Site Coefficient, FAl 1.2 <br /> Design Site Class Short Period Spectral Acceleration,Sos(percent g) 95.8 <br /> 1s Period Spectral Acceleration,Si(percent g) 42.6 <br /> Site Coefficient, Fvl 2.4 <br /> Design Site Class 1s Period Spectral Acceleration,So>(percent g) 68.2 <br /> Notes: <br /> 1 The site coefficients FA and Fv provided are only valid for structures that are not damped or selsmically isolated.The calculated <br /> values for Sos and Sol depend on these coefficients. <br /> Seismic Hazards <br /> The Puget Sound region is a seismically active region.Seismicity in this region is attributed primarily to the <br /> interaction between the Pacific,Juan de Fuca and North American tectonic plates.The Juan de Fuca Plate <br /> is subducting beneath the North American Plate. Each year 1,000 to 2,000 earthquakes occur in <br /> Washington and Oregon. However, only five to 20 of these are typically felt because most recorded <br /> earthquakes are smaller than magnitude 3. <br /> Potential seismic hazards from earthquakes include ground shaking, surface fault rupture, liquefaction, <br /> and lateral spreading.We evaluated the likelihood of each of these hazards at the site. <br /> Liquefaction Potential <br /> Liquefaction refers to the condition by which vibration or shaking of the ground, usually from earthquake <br /> forces, results in the development of excess pore pressures in saturated soils with subsequent loss of <br /> strength in the deposit of soil so affected. In general,soils susceptible to liquefaction include very loose to <br /> medium dense clean to silty sand and some silt soils,and that are below the groundwater level. <br /> The evaluation of liquefaction potential and settlement is a complex procedure and is dependent on <br /> numerous site parameters,including soil grain size,soil density,site geometry,static stress,and the design <br /> ground acceleration.Typically,the liquefaction potential of a site is evaluated by comparing the cyclic stress <br /> ratio(CSR), which is the ratio of the cyclic shear stress induced by an earthquake to the initial effective <br /> overburden stress, to the cyclic resistance ratio (CRR), which is the soil resistance to liquefaction. <br /> Estimation of the CSR and the CRR were completed using empirical methods(Youd,et al.2001). Estimated <br /> ground settlement resulting from earthquake-induced liquefaction was analyzed using empirical <br /> procedures based on correlations from the standard penetration test(SPT)data obtained while drilling our <br /> borings(Tokimatsu and Seed 1987; Ishihara and Yoshimine 1992). <br /> The results of our analyses indicate that portions of the alluvial deposits encountered at the site and which <br /> are below the groundwater level have a significant potential for liquefaction during a design earthquake <br /> event. We estimate settlement due to liquefaction during the design seismic event will range from about <br /> 6 to 14 inches for the free-field condition. <br /> GEoENGINEER� August3,2018 Page7 <br /> rile No.0643-015-00 <br />