Identification of Keddara dam behavior during Boumerdes earthquake on May 21, 2003

An earthquake, with magnitude of 6.8, shocked Keddara rockfill dam on May 21, 2003 in Algeria. Accelerometers array that had been installed on the site recorded the motions at the crest, the abutments and in free field. An analysis of accelerograms recorded during and after the main shock provided the basis for an analysis of the seismic behavior of this dam. The vibrational modes excited during the earthquake were estimated. A spectral analysis indicated that the fundamental mode of the dam excited during the main shock corresponds to a longitudinal mode. In addition, a simulation of the seismic response of Keddara dam to varying earthquake ground motions in the transversal direction is proposed. A space time earthquake ground motion model that account for both coherency decay and seismic wave propagation is used to specify the support motions. Many analyses on seismic behavior of embankment dams have shown the need to consider differential ground motion along the canyon width; this study illustrates the necessity of considering the spatial varying earthquake motion in the transversal direction. Indeed, the uniform input motion overestimates the crest response drastically.