Seismic dam failures

Flooding can result from dam failures (upstream or downstream) caused by seismic events or from the consequences of seismic events such as a landslide into a reservoir. Failures may occur of both human made dams and naturally created water impounding structures. 

The seismic analysis of dams requires consideration of the dynamic loading furthermore, a detailed stability analysis requires proper documentation of the condition of the structure. Inspection reports issued by the appropriate national technical bodies should be used in the stability analysis. Additional data should include the results of strength tests of the dam foundation areas, field surveys and inspection by other bodies, together with pertinent data collected by instrumentation installed at the dam site. 

For the seismic analysis of each dam, an appropriate earthquake (see Ref. [2]) should be derived, specifically for the dam site or the landslide site. 

The possibility of the failure of two or more dams being caused by the same seismic event should also be taken into consideration. If there is a potential for common failure, the possible simultaneous arrival of the flood peaks should be considered, unless it can be demonstrated that the times of travel of the peaks are sufficiently different for their simultaneous arrival to be impossible. 

Most of the procedures described in the previous subsection may be applied to seismic failures. However, for failure models for hydrological dam failures it is assumed that the dam is overtopped by water, while for seismic failure this does not necessarily occur. The mode and degree of failure should be postulated by using conservative judgement based as far as possible on stability analysis. 

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