3D modeling of near-field ground motions and deformation in dynamic rupture simulations of the 2019 Ridgecrest earthquake including fault zone and fault roughness effects

Nico Schliwa, Alice-Agnes Gabriel, & Yehuda Ben-Zion

Published September 10, 2023, SCEC Contribution #12909, 2023 SCEC Annual Meeting Poster #182

We present large-scale modeling of near-field ground motion parameters and deformation in dynamic rupture simulations of the 2019 Mw 7.1 Ridgecrest earthquake. We include an observationally constrained shallow low-velocity fault zone and band-limited self-similar fractal fault roughness. Fault roughness induces geometric and small-scale stress perturbations, which can generate deterministic high-frequency radiation. The model also incorporates a strong velocity weakening rate-and-state friction law, complex non-vertical fault geometry, 3D velocity structure, high-resolution topography, 3D initial stress distribution, off-fault plasticity, and viscoelastic attenuation (Taufiqurrahman et al., Nature, 2023).

We examine different ground motion parameters (PSA, PGA, PGV, PGD) and compare them with observed seismograms and GMPEs. We are especially interested in the near-field, closer than 10 km to the rupture, where real observations of strong ground motions are sparse and GMPEs are poorly constrained. The modeled ground motion parameters exceed the empirical predictions close to the rupture zone (< 2 km), which is only partly explained by effects of the low-velocity fault zone. We discuss which (if any) surface observations can constrain the dynamics of earthquakes, in particular for rapidly decaying near-field source effects. For each examined parameter, we show how the values inferred from the surface compare to their equivalents inferred within the volume. We also analyze the distributions of plastic vs. elastic off-fault deformation and their partitioning into volumetric and shear components.

Citation
Schliwa, N., Gabriel, A., & Ben-Zion, Y. (2023, 09). 3D modeling of near-field ground motions and deformation in dynamic rupture simulations of the 2019 Ridgecrest earthquake including fault zone and fault roughness effects. Poster Presentation at 2023 SCEC Annual Meeting.


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