What is the purpose of seismic instrumentation in dams?

To record the actual ground motion and the dynamic response of the dam during an earthquake, aiding in post-earthquake safety evaluation.

What are the main instruments recommended by this code?

Strong motion accelerographs, seismographs (for micro-tremor studies), and structural response recorders.

Where should accelerographs be placed on a concrete gravity dam?

Typically at the foundation (bedrock), at an intermediate gallery (mid-height), and at the top (crest) to measure amplification.

IS 4967

: 1968

Recommendations for seismic instrumentation for river valley projects

CurrentSpecializedGuidelinesWater Resources · Earthquake Engineering

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This standard provides guidelines for the selection, location, installation, and maintenance of seismic instruments in river valley projects, particularly large dams. It ensures that ground motion and structural response during earthquakes are accurately recorded for safety evaluation and future design improvements.

Recommendations for seismic instrumentation for river valley projects

Quick Reference Values

recommended accelerographs concrete damMinimum 3 (Base, Mid-height, Crest)

recommended accelerographs earth damMinimum 3 (Foundation, Berm, Crest)

target dam height for instrumentationTypically > 100m or situated in active seismic zones

Practical Notes

Instruments must be planned during the design phase so that necessary niches, galleries, and embedded conduits are provided during construction.

The base accelerograph should be installed directly on sound bedrock to capture the true input ground motion without structural interference.

Regular maintenance and battery checks are critical, as these instruments may sit dormant for years but must function flawlessly during an unpredictable seismic event.