Carlos Le
Research Mentor: Fernando Garcia
Mentor Department: Civil and Environmental Engineering, Engineering
Author(s): Carlos Le, Fernando Garcia, Chenyu Li
Session: Session 3 (11:00 AM – 11:50 AM)
Presentation Type: Poster 140
Abstract
Precariously Balanced Rocks (PBRs) can provide valuable insight into earthquake history in regions of low seismicity, such as the eastern US. By analyzing the dynamic response and fragility of existing PBRs in the eastern US, we can determine probabilities that an earthquake of certain magnitude has occurred in a previous time period. We create models of the boulders and expose them to ground movements to determine the probability of the boulder toppling given an earthquake ground motions of varying amplitude and frequency content. This research primarily focuses on the creation and validation of computational boulder models. By running simulations of boulder dynamic responses, we can calibrate the natural frequency and restitution of modeled boulders against push tests performed on real boulders. The simulations result in a time series which when compared against real world data allows us to compare the accuracy of our boulder model to the real PBR. Subjecting the boulder models to a large number of different ground motions allows us to assess the fragility of the boulder given different peak ground accelerations and peak ground velocities. By creating a curve separating toppling and not toppling, we can develop fragility models for boulder toppling given these aforementioned ground motion characteristics. This final result allows us to determine the probability of an earthquake of a certain magnitude occurring in the last 14,000 years, i.e., since the time the boulders were deposited during the last ice age. Given the uncertainty in the contact geometry between the boulder and its platform, the models are first validated against shake table experiments with rectangular concrete blocks.
