Generation of Broadband Ground Motion from Dynamic Rupture Simulations: A Group Modeling Approach towards better Characterizing Seismic Hazard for Engineering Applications

Kyle B. Withers, Shuo Ma, Yongfei Wang, Thomas Ulrich, Dunyu Liu, Benchun Duan, Alice-Agnes Gabriel, Jean-Paul Ampuero, Elif Oral, Luis A. Dalguer, Christine A. Goulet, & Domniki Asimaki

Published August 13, 2021, SCEC Contribution #11344, 2021 SCEC Annual Meeting Poster #035

We work towards improving methods of simulating earthquake ground motions for seismic hazard applications by continuing a newly formed group modeling effort that incorporates features of the earthquake fault and rupture (e.g., through complex fault geometry, stress heterogeneity, etc.) that are known to influence earthquake ground motions. Our investigation analyzes how earthquake rupture characteristics influence ground motion behavior and compares these synthetically generated ground motions with ground motion models (GMMs). We work to determine conditions for acceptance of broadband synthetic ground motions, towards the goal of ultimately supplementing empirical relations with simulation-derived information.

This project builds a synthetic database of ground motion amplitudes from a diverse range of initial conditions and modeling techniques. We achieve this by first creating a database of strike-slip faulting dynamic rupture simulations at frequencies computationally accurate up to ~3 Hz (and higher where computationally feasible). The resulting broadband ground motions are compared with estimates from empirical ground motion models (GMMs). We focus on Mw ~5-7 events and compute ground motions at distances up to 20 km from the source and compare median spectral accelerations across a range of periods. Additionally, we analyzed the synthetic ground motion variability (isolated in terms of intra-event) as a function of both distance and period.

We find the aggregated level of ground motion compares well with the GMM’s predictions in terms of both distance decay and median ground motion at long and intermediate periods, but some methods have lower than expected amplitudes at shorter periods. We observe that intra-event variability is highly dependent on hypocenter location, resulting from azimuthal changes in ground motion amplification. In addition to modeling ground motion, we also keep track of fault displacement along the surface trace of the fault, which ensures that we don’t create unrealistic source events that may neglect constraints of physical ruptures, a possibility if efforts of source generation are pursued in isolation. Finally, we plan to make our database publicly available for use by a variety of other end-users and investigations.

Key Words
dynamic rupture

Citation
Withers, K. B., Ma, S., Wang, Y., Ulrich, T., Liu, D., Duan, B., Gabriel, A., Ampuero, J., Oral, E., Dalguer, L. A., Goulet, C. A., & Asimaki, D. (2021, 08). Generation of Broadband Ground Motion from Dynamic Rupture Simulations: A Group Modeling Approach towards better Characterizing Seismic Hazard for Engineering Applications. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions