3-D Dynamic Analysis of Precariously Balanced Rocks Under Earthquake Excitation

Hundreds of Precariously Balanced Rocks (PBRs) exist in California. Since these rocks have been precariously placed for thousands of years, they can help in constraining the range of PGV (peak ground velocity) and frequency content of the ground motions that could not have occurred at this location during the time that the rock has been precariously positioned. We are developing 3-D models (with accurate rock-pedestal contact interface) of some of the PBRs that have been imaged using Terrestrial Laser Scanning (TLS) techniques. We use Rigid body dynamics to solve for the dynamic response of the rock models subjected to idealized and earthquake ground motions intensities to arrive at probabilistic constraints on region-wide ground shaking intensity by combining the results of this study with cosmogenic dating of these rocks. Such analyses could help quantify seismic hazards and validate ground motion simulations