Nonuniform Ground Motion Effects at Pacoima Dam

by John Hall and Steven Alves

Hall, John, and Steven Alves (2003). Nonuniform Ground Motion Effects at Pacoima Dam. SMIP03 Seminar on Utilization of Strong-Motion Data, p. 67 - 86.

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A magnitude 4.3 earthquake was recorded on an array of accelerometers at Pacoima Dam on January 13, 2001. The records are used for two purposes: (1) to analyze the effects that canyon topography has on the ground motion along the abutments, and (2) as input for a system identification study, leading to a calibrated finite element model of Pacoima Dam. The quantified amplification and time delay characteristics of the 2001 abutment motions serve as a basis for generating records to replace ones that went off-scale during the 1994 Northridge earthquake. These generated records were then used in the finite element model to verify that nonuniform ground motion caused by the topography has a significant impact on the dam response. Forced vibration tests were also conducted in July/August 2002.