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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, Alice-Agnes Gabriel, Luis A. Dalguer, Thomas Ulrich, & Christine A. Goulet

Published August 6, 2020, SCEC Contribution #10277, 2020 SCEC Annual Meeting Poster #198

In areas of infrequent seismicity or where geologic structures (e.g., sedimentary basins) complicate seismic wave propagation, earthquake ground-motion simulations provide one approach to improving the accuracy of ground-motion predictions for seismic hazard analyses. However, most current methods for simulating earthquake ground motions ignore important features of the earthquake rupture and typically employ stochastic approaches at high frequencies (> ~1 Hz). We work toward improving methods for simulating earthquake ground motions for seismic hazard applications via a group modeling effort that incorporates features of the earthquake fault and rupture (e.g., through complex fault geometry, stress heterogeneity, and friction conditions and constitutive relations) that have been demonstrated from both observations and numerical simulations to affect resulting ground motions.

We create a database of dynamic rupture simulations (a fully deterministic, physics-based approach dependent on initial friction and stress conditions along a fault to forward simulate rupture and resulting ground motions) of strike-slip earthquake mechanisms at frequencies computationally accurate up to ~3 Hz (and higher where computationally feasible). The resulting broadband ground motions are validated by comparing with empirical trends predicted by leading ground motion models (GMMs). We focus on the magnitude range of Mw ~5 up to Mw 7 at distances up to 20 km from the source, for material models representative of hard rock sites, comparing median spectral accelerations across a range of periods. Additionally, we analyze the synthetic ground motion variability (isolated in terms of both intra- and inter-event) as a function of both distance and period. Thus far, we are finding that our ruptures agree with empirical models of magnitude-area relations and have similar distance trends of median ground motion levels and intra-event variability of existing GMMs.

We aim to build a synthetic database of ground motion amplitudes from a diverse range of initial conditions and modelling techniques. Additionally, we also keep track of final fault displacement along the surface trace of the fault. We intend to make our database publicly available, for use by a variety of other end-users and investigations.

Withers, K. B., Ma, S., Wang, Y., Gabriel, A., Dalguer, L. A., Ulrich, T., & Goulet, C. A. (2020, 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 2020 SCEC Annual Meeting.

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