Do 3D Dynamic Rupture Models Capture the Variability in Long-Period Velocity Pulses? Insights from the 2023 Mw 7.8 Kahramanmaraş Earthquake

Rachel Preca Trapani, Mathilde Marchandon, Kadek Hendrawan Palgunadi, Baoning Wu, Ming-Hsuan Yen, Fabrice Cotton, Alice-Agnes Gabriel

Capturing ground motion variability, especially in near-fault long-period velocity pulses, is a key challenge for seismic hazard assessment. Observations from the 2023 Mw 7.8 Kahramanmaraş, Türkiye earthquake reveal substantial variability in the near-fault pulses’ orientation, period, and amplitude. Physics-based dynamic rupture simulations provide a unique framework for investigating the physical mechanisms responsible for this variability. Here, we systematically investigate the effect of fault geometry and on-fault heterogeneities in a suite of 3D dynamic rupture simulations of the 2023 Mw 7.8 Kahramanmaraş, Türkiye, earthquake. We compare dynamic rupture scenarios that separately incorporate large-scale fault waviness, fractal fault roughness, heterogeneous critical slip-weakening distance, heterogeneous dynamic friction, and supershear versus subshear initiation, each resolving up to at least ~1 Hz. We systematically analyse the influence on rupture dynamics, frequency content, and long-period pulse variability, while ensuring all models have comparable seismic moment rate release. While all models capture near-fault pulse amplitude variability, supershear initiation and fracture energy heterogeneity exert the strongest influence on pulse period and orientation. Despite added complexity, most modelled pulses remain predominantly fault-normal, contrasting observed broader ranges of orientations, but supershear rupture speed locally increases variability in pulse orientation. The four other distinct on-fault heterogeneities all fail to broaden the modelled orientation distribution, suggesting that this aspect of near-fault pulse variability is not controlled by on-fault complexity alone. It points instead to processes beyond main-fault rupture, including off-fault damage, fault zone structure or site effects, as necessary ingredients for realistic, non-ergodic ground-motion models and physics-based seismic hazard assessment.