Ground displacement investigations in downtown Salt Lake City, Utah using the cone penetrometer

This paper discusses ground displacement investigations in downtown Salt Lake City, Utah using cone penetrometer tests (CPT) and shows how this device can be used for fault studies in urban areas. Previous geologic mapping and evaluations in this area have identified three areas of prehistoric ground displacement: (1) lateral spread deposits (clsp Holocene to middle Pleistocene) located between 300 East and 600 East Streets (2) clsp deposits near the Old Metropolitan Hall of Justice (Osmond et al., 1965) and (3) ground displacement at the expansion of the Salt Lake Convention Center (Simon-Bymaster, 1999; Kleinfelder, 1999; Cotton, Shires and Associates, 1999; Black et al, 2003; Korby and McCormick, 1999). To further define the extent of these ground displacement zone(s) and explore their relation with the southern end of the Warm Springs fault, CPT investigations were performed in a west-east line along 400 South Street. A subsurface cross-section developed for this line suggests a significant vertical displacement (approximately 8.7 m) in late Pleistocene and Holocene lacustrine and alluvial deposits between adjacent CPT soundings along 400 South Street. The amount and location of this displacement suggests that the offset is in part associated with the Warm Springs fault. In addition, liquefaction analyses of the CPT soundings for a M7.0 earthquake suggest that potential liquefaction induced settlement will not exceed about 0.1 m and that lateral spread displacement will be negligible in this area.