Seismic instrumentation is recognized as a valuable tool to monitor and record the behavior of dams when an earthquake occurs and inform decision-making during an emergency. Although the focus in the dams industry has been on strong motion data, and the motivation for installing many of the seismometers has primarily been for situational awareness, there’s tremendous value in weak ground motion recordings to characterize the seismic hazard at a dam site. In seismic hazard assessments, the standard of practice is to account for site conditions through site adjustment factors that are based on global ground motion datasets. On the other hand, the state of the art in ground motion modeling is represented by analysis techniques that characterize the site response directly from ground motion recordings obtained from a seismic instrument installed at the site. This paper presents the results from an applied research project focused on understanding how the characterization of site effects may change at a single rock dam site with the future acquisition of on-site recordings. The project included a close examination of ground motion recordings at rock sites in California, use of a new open-source ground motion database, and calculation of site adjustment factors from on-site recordings at several well-recorded rock sites in California. Challenges in the development of the adjustment factors are shared and comparisons are made with site adjustment factors developed from global datasets to illustrate the benefits of seismic instrumentation, the value in weak ground motion data, and the potential impact on seismic hazard assessments.
