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I <br /> October 2, 1998 <br /> Project Na. KE98375G <br /> I <br /> � <br /> II. GEOLOGIC HAZARDS AND MPTIGATIONS ' � <br /> . � <br /> , <br /> 1 <br /> The following discussion of potential geologic hazards is based on the geologic and ground � <br /> water conditions as observed and discussed herein. <br /> 5.0 SEISMIC HAZARDS AND RECOMMENDED MITIGATION <br /> Earrhquakes cecur in the Puget Lowland widi great regularity. Fortunately, the vast majority <br /> of these events are small and are usually not felt Uy man. Howe�er, lazge earthquakes do <br /> occur as evidenced by the 1949, 7.? magnitude event and the 1965, 6.5 magnicude event. 'The <br /> 1949 earthquake appears to have been the lugest in this area during recorded history. <br /> Evaluation of earthquake return rates indicate that an earthquake of the roagnicude between 5.5 <br /> and�(,p ►ikeiy willl ccur within che next 8 to 12 years. _ <br /> Generally, there are four rypes of potential geologic hazards associated with large seismic <br /> events: 1) surficial ground rupture; 2) seismically induced landslides; 3) liquefaction; and 4) <br /> ground motion. The potential for each of these hazards to adversely impact the proposed <br /> projectis discussed below. <br /> 5 1 Surficial Ground Runture <br /> Genetally, the largest earthquakes which have occurred in the Puget Sound area are sub-crustal <br /> events with epicenters ranging from 50 to 70 kilometers in depth. For this reason, no su�cial <br /> faulting, or earth rupture, as a result of deep, seismic activiry has been documented to date, in <br /> the area of the subject site. Therefore, it is our opinion, based on the existing geologic data, <br /> that the risk of surface rupture impacting the proposed project is low. <br /> 5 2 Seismicallv Induced I.andslides <br /> Based on the encountered stratigraphy and our visual reconnaissance, it is our opinion that the <br /> risk of seismically induced landslides itnpacting the site is low. The site is underlain by dense, <br /> granular soils, as described previously. These materials should remain relatively intact during <br /> potential strong motion seismic events, and we do not andcipate that deep-seated landsliding <br /> would affect the site. <br /> 5 <br />