The Earthquake Monitoring System for Dams of a reservoir in China

In this paper, the authors give a brief introduction to the earthquake monitoring system newly developed for two dams of a reservoir in North China. The two embankment dams are 66, 56 meters high and 960, 1008 meters long respectively. One of the dams suffered from severe landslide because of the 1976 Tangshan Earthquake, the design PGA of this site is set to 0.25g. Because of the complexity, it is quite difficult to predict the dam earthquake response by numerical simulation, thus the recorded motion data will be very useful for the dam dynamic design and seismic safety assessment. In order to monitor the earthquake response of the two dams, two unique sets of new type earthquake monitoring system are developed and installed in February 2003. Each of the system consists of a Data Logger (16 bit resolution, synchronous 18 channels) and 16 Force Balanced Accelerometers (0-50Hz, 120 dB). Accelerometers are installed at the bottom, middle as well as the top of the dams. Two gears of sensitivity are set for the accelerometers; one is for strong motion recording and the other for microtremor measurement. The microtremor data can be used for seismic safety evaluation of the dams.