Dam Safety: Use of Seismic Monitoring Instrumentation in Dams

Seismic instrumentation of dams and reservoirs sites is accepted today as a valuabletool to understand significant seismic hazards facing existing dams or future planeddams. With the advent of digital seismic accelerometers and recorders, it can nowbe used today as an integral part of dam safety monitoring systems. Outputs of theseinstruments help in understanding the dynamic response of dams during earthquake,assessing the damage caused by such events and determining required upgradingworks necessary for existing dams and designing of safer dams in the future.Measuring and recording by strong motion seismographs covers the induced PeakGround Acceleration (PGA), velocity and displacement recorded on time scale toindicate the intensity and frequency of ground vibration at the site during seismicevents. Seismometers for such measurements and recordings have undergoneconsiderable evolution and there exist today a variety of these instruments with highdegree of refinement which can even provide for remote sensing. In this work, thisdevelopment is outlined and examples of seismic instrumentation in strategic damsare described. Damages to actual concrete and embankment dams of various typesare described indicating the associated PGAs experienced during the mentionedearthquakes. Damages in the form of cracking, increased seepage, additionalsettlements and displacements are described to show type and extent of possibleconsequences of such events on dams. The reached conclusion is that seismicinstrumentation systems are desirable and highly recommendable for all types ofdams; existing and future ones and their high cost is justified by the service theyprovide.