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6 I Port of Everett—South Terminal Wharf& Electrical,Upgrades—Phase 2 <br /> earthquakes. Deep,intraslab earthquakes tend to be felt over larger areas than shallower interface events, <br /> and generally lack significant aftershocks. <br /> Crustal Sources. Recent fault trenching and seismic records in the Puget Sound area clearly indicate a <br /> distinct shallow zone of crustal seismicity.The primary area of interest is the Seattle fault zone,which <br /> forms the southern boundary of the Seattle basin,and consists of an approximately 50-to 75-km-long <br /> southern-dipping thrust fault system that extends about 20 km deep.The project site is located about <br /> 45 km north of the northern splay of the Seattle fault zone(Figure 8).An additional source of crustal <br /> seismicity in the Puget Sound region is the Southern Whidbey Island fault system (SWIF).The extent and <br /> characteristics of the SWIF are less well-known than the Seattle Fault system,but recent LIDAR imaging, <br /> fault trenching,and geologic mapping have characterized the SWIF as an approximately 5-to 10-km-wide <br /> zone of relatively steep, northeast-dipping faults,that can generate up to magnitude-7.4 events.The <br /> northwest-trending SWIF extends about 100 km from about 5 km northwest of Redmond to the eastern <br /> extent of the Strait of Juan de Fuca.The project site lies about 6 km northeast of the northern splay of the <br /> SWIF. <br /> Fault Surface Rupture <br /> The project site lies about 6 km northeast of the northern splay of the South Whidbey Island Fault System <br /> (as shown on Figure 8).There are not any known faults directly underlying the site.Therefore,the risk for <br /> surface rupture is low. <br /> Site Class and Shear Wave Velocity <br /> Refraction microtremor(ReMi)and multichannel analysis of surface wave(MASW)surveys were <br /> completed by Global Geophysics on August 27,2016(Attachment 1).The results of these surveys were <br /> used for site class determination and to use in our site response analysis.The MASW based S-wave profile <br /> is provided on Figure 9.The measured profile had a Vs30(weighted average shear wave velocity in the <br /> upper 30 meters or 100 feet)of 1,042 feet per second.This Vs30 corresponds to Site Class D. <br /> The shear wave velocity measurements from the SCPTu were completed by Insitu Engineering on <br /> August 19,2016.The results of these measurements are primarily in the dredged fill,and are also provided <br /> on Figure 9, but were not used for site class determination as the measurements were taken further <br /> upland from the wharf than the MASW measurements. <br /> Because the site contains potentially liquefiable soil, it is classified as Site Class F under ASCE 7-10.ASCE <br /> 7-10 requires a site-specific ground response analysis to determine seismic parameters for Site Class F soils <br /> if the period of the structure is greater than 0.5 seconds. In accordance with ASCE 7-10(Section 21.3),our <br /> recommended spectrum will be compared to the code-based Site Class E spectrum. <br /> Seismic Basis of Design <br /> At the request of KPFF,six seismic hazard levels were considered in our analysis,which are summarized in <br /> Table 3.The hazard level corresponding to the"life safety protection" performance level is the Design <br /> Earthquake(DE),which is taken as two-thirds of the 2,475-year hazard level. Response spectra for these <br /> 19232-01 A <br /> December 6,2017 Y <br /> H/.1RTO?OWSER <br />