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( <br /> � Subsurjace Ezplo�at�on, Geologic Hazard and <br /> Sna-lale Skills Cenrer Add'uian Prelimirwry Geotechnical Eng'u�eerin8 Report <br /> Geologic Hatnrds and Mitigatinns <br /> Everett, Wathingron <br /> III. GEOLOGIC HAZARDS AND MITIGATIONS <br /> I1'he following discussion of potential geologic hazards is based on che geologic and ground <br /> Iwater conditions as observed and discussed herein. <br /> I 5.0 SLOPE STABILITY ASSESSMENT <br /> There were no significant slopes on the site. Therefore, it is our opinion that the risk of <br /> shallow and deep-seated landslides is low for static and seismic conditions, and no mitigation <br /> measures aze required. <br /> � 6.0 SEISMIC HAZARDS AND MITIGATION <br /> Earthquakes occuc in the Puget I,owland with great regulazity. The vast majority of these <br /> events are small, and are usually not felt. However, la:ge earthquakes do occur as evidenced <br /> I by the 1949, 7.2-magnitude event; the 19P6�5S o havegbeen the largestnm this azea'dur'g <br /> magnitude event. The 1949 eartl�quake app <br /> recorded history. Evaluation of return rates indicates thatr�ea�th4uake of the magnitude <br /> between 6.0 and 7.0 is likely within a given 20-to 40-year pe <br /> Generally, ihere aze four types of potential geologic hazards associated with luge seismic <br /> i events: 1) surficial ground rupture, 2) seismicaily induced landslides, 3) liquefaction, and <br /> ' 4) ground motion. The potential for each of these hazards to adversely impact the propose8 <br /> project is discussed below. <br /> 6 1 Surficial Ground Rupture <br /> The neuest known and �.vell-stadied fault trace to the project site is the South Whidbey Island- <br /> � I,ake Alice Fault. Data pertaining to che South Whidbey Island-Lake Alice Fault aze not well <br /> documented, but no evidence of surficial ground rupture has been noted. <br /> The recurrence intervals for movement along this fault system aze still unlmown, aithongh theY <br /> aze hypothesized to be in excess of several thousand yeazs. Due to the suspected long <br /> recunence intervals and the distance to this fault zone, the potential for surficial ground <br /> rupture is considered to be low during che expected life of the structures, and no mitigarion <br /> efforu beyond compiying with the current (2006) International Building Cade (IBC) aze <br /> recommended. <br /> ASSOC(ATFJ)F.AR7N SCIF�CES, MC. <br /> /we 11, z0�8 Page 5 <br /> F,/W-F.F�'1713A5-Pro/�a'���131EE�µ'P <br />