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Eugene City Hall R32.19.04 Rev. B. September 9, 2003 <br /> <br /> 3.05E-03 0.103 <br /> 1.96E-03 0.145 <br /> 1.03E-03 0.203 <br /> 4.53E-04 0.284 <br /> 1.76E-04 0.397 <br /> 5.93E-05 0.556 <br /> 1.65E-05 0.778 <br /> 3.67E-06 1.09 <br /> 6.59E-07 1.52 <br /> 9.09E-08 2.13 <br /> Table 4-1. Tabulated data for Figure 4-1 <br /> <br /> Given the occurrence of an earthquake, there are four hazards that might occur: ground <br /> shaking, liquefaction (and related types of ground failure), landslide and surface faulting. <br /> These hazards are further described below (largely adopted from (Dames and Moore <br /> 1995) - no site subsurface investigations were performed as part of the current effort: <br /> <br /> o Ground shaking hazard. This is covered in Figure 4-1 and Table 4-1. For design <br /> purposes, a broad-banded response spectra suitable for firm soils sites tied to the <br /> PGA levels of Table 4-1 is appropriate. <br /> <br /> o Liquefaction. The subsurface conditions in the Eugene area are controlled by the <br /> ancient courses of the Willamette and McKenzie Rivers. Historical courses of the <br /> rivers scoured relatively deep channels in the underlying bedrock, where were <br /> filled gradually and episodically by alluvial deposits. Most of Eugene is underlain <br /> by older alluvial deposits which have been locally eroded and replaced by <br /> younger alluvium along the present courses of the Willamette and McKenzie <br /> Rivers. The older alluvium in the valley floor is generally capped by a surficial <br /> layer of wind-deposited silt. In the downtown area where City Hall is located, the <br /> subsurface conditions generally consist of 5 to 15 feet of silty soils underlain by <br /> gravel and cobble deposits of the older alluvium. The foundation system for City <br /> Hall is assumed to extend through the silty layer and is established on the gravelly <br /> soils. The older alluvium generally consists of dense silty and sandy gravel with <br /> cobbles. Soft soil conditions are not indicated at City Hall. Given these <br /> conditions, the site has a very low susceptibility to liquefaction-induced <br /> settlements or lateral spread. <br /> <br /> o Landslide. The site geology is not considered prone to landslide. <br /> <br /> o Surface Faulting. Surface faulting is not considered likely for this site for <br /> subduction zone earthquakes. There are no known active or potentially active <br /> faults that traverse the site. <br /> <br /> G&E Engineering Systems Inc. Page 26 <br /> <br /> <br />