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Validating Physics-engine Simulations of Precariously Balanced Rocks for Hazards Applications

Description: 

Precariously balanced rocks in the landscape may be used to constrain maximum shaking intensity over timescales at which damaging earthquakes recur. Developing such valuable data requires estimating a precariously balanced rock’s fragility, which we define as the probability of toppling as a function of one or more intensity measures. At present, fragilities are typically calculated using empirical equations derived from a combination of shake-table data and numerical modeling results. These equations are limited to a few geometric parameters, rather than a realistic representation of a real rock, but simplified geometric representations have been necessary because of the complexity and computational costs of discrete-element simulations. Recently, Chen et al. (2024) developed the Virtual Shake Robot (VSR), a physics-engine approach for simulating both toppling and large-displacement dynamics of precariously balanced rocks, which promises accuracy and efficiency. Like other models, the VSR requires careful selection of macro-physical parameters. The VSR was designed as the digital twin of a real-world shake table, and the VSR has been tested against a small number of shake-table experiments. Here, we extend the validation of the VSR with a larger ensemble of shake-table data. Klaboe et al. (2018) conducted 312 shake-table experiments, where five concrete blocks were excited by variously scaled waveforms from six earthquakes. For each experiment, displacement was recorded with video and optical image tracking. We reproduce these experiments virtually, using the VSR, and find that 75% of the toppling outcomes agree. Disagreements typically occur at shaking intensities where previously published fragility models indicate an intermediate probability of toppling. We investigate the causes of disagreements by testing parameter sensitivities and dynamic responses of the blocks.

Z. Chen et al., 2024. Virtual Shake Robot: Simulating dynamics of precariously balanced rocks. doi:10.26443/seismica.v3i1.692

K. Klaboe et al., 2018. Seismic response of rocking blocks. Earthquake Spectra, 34(3), pp. 1051-1061.

Session: The Landscape Record of Earthquakes and Faulting - III

Type: Oral

Date: 4/16/2026

Presentation Time: 03:15 PM (local time)

Presenting Author: Devin McPhillips

Student Presenter: No

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