Seismic Stability of Upper San Leandro Dam

The dam was analyzed using stability analysis techniques based upon postulated ground motion patterns, dynamic as well as static soil properties, and saturation patterns. The study was initiated because of concern over safety considerations for such dams in seismically active areas. The near catastrophe of the Lower San Fernando Dam in the San Fernando earthquake of February, 1971, highlighted the vulnerability and the consequence of failure of such structures. Several reservoir water levels, a range of material properties, and three postulated earthquake motions originating on two major faults were considered. The significant results of the investigation are summarized in two figures: one which shows the effect on stability of variations in dynamic modulus values on the potential behavior; the other shows the effect on stability of variations in maximum rock acceleration.