Dam Safety: Use of Seismic Monitoring Instrumentation in Dams

Seismic instrumentation of dams and reservoirs sites is accepted today as a valuable tool to understand significant seismic hazards facing existing dams or future planed dams. With the advent of digital seismic accelerometers and recorders, it can now be used today as an integral part of dam safety monitoring systems. Outputs of these instruments help in understanding the dynamic response of dams during earthquake, assessing the damage caused by such events and determining required upgrading works necessary for existing dams and designing of safer dams in the future. Measuring and recording by strong motion seismographs covers the induced Peak Ground Acceleration (PGA), velocity and displacement recorded on time scale to indicate the intensity and frequency of ground vibration at the site during seismic events. Seismometers for such measurements and recordings have undergone considerable evolution and there exist today a variety of these instruments with high degree of refinement which can even provide for remote sensing. In this work, this development is outlined and examples of seismic instrumentation in strategic dams are described. Damages to actual concrete and embankment dams of various types are described indicating the associated PGAs experienced during the mentioned earthquakes. Damages in the form of cracking, increased seepage, additional settlements and displacements are described to show type and extent of possible consequences of such events on dams. The reached conclusion is that seismic instrumentation systems are desirable and highly recommendable for all types of dams; existing and future ones and their high cost is justified by the service they provide.