Earthquakes affect all structures, elements and equipment of large storage dams at the same time. According to today's seismic performance criteria it is accepted that the dam body can be damaged during the safety evaluation earthquake. However, the dam must be able to safely store the reservoir and it must be possible to control or lower the reservoir after the safety evaluation earthquake. This means that the low level outlets, gated spillways and all related power supply and control facilities must be operable after the safety evaluation earthquake. Dam engineers are familiar with seismic actions, however, the designers of hydro-mechanical and electro-mechanical equipment and components follow their own guidelines and criteria, which may not be fully compatible with those of the dam engineers. The seismic design and performance criteria low level outlets and gated spillways of large storage dams are presented. The seismic performance of such facilities during recent earthquakes is discussed. Furthermore, attention is drawn to the fact that the seismic hazard is a multiple hazard which does not only include ground shaking. Finally, the construction of crest spillways in concrete dams, where large amplification of the ground motion is possible is addressed.
