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<p>Low-velocity fault zones, predominantly located in the shallow crust (0–5&#xa0;km depth), amplify localized earthquake-triggered ground shaking, thereby exacerbating the vulnerability of surface structures. Understanding the influences of fault zones on seismic wave propagation, including their effects&#xa0;on both translational and rotational ground motions, is necessary for seismic hazard assessment. We first establish a 2D model based on the Binhai fault zone in the Taiwan Strait and a Hualien M<sub>W</sub> 6.1 earthquake and then use the staggered-grid finite difference method to simulate seismic wavefields of translational (X, Z) and rotational Y (Ry) components in models with and without a normal fault zone. By evaluating amplitude and spectral characteristics of ground motion across observation positions along the fault, we investigate the responses of translational and rotational component motions to the fault zone. Results demonstrate spatially heterogeneous amplification and attenuation effects and differential responses between seismic rotational and translational motions: <i>(i)</i> The fault zone amplifies ground motions asymmetrically on its northwestern (NW) and southeastern (SE) sides (up to 300% and 100% amplification, respectively), while attenuating amplitudes (40–70% reduction) in its overlying central region. <i>(ii)</i> Near the fault (≤ 10&#xa0;km), Ry-component amplitudes exceed translational components by 20–80%, but this enhancement diminishes, becoming 20–120% weaker at farther distances (~ 10–30&#xa0;km). <i>(iii)</i> High-frequency Ry signals exhibit stronger amplification and weaker attenuation compared to translational components, highlighting frequency-dependent fault-zone dynamics. These findings underscore the necessity of incorporating rotational ground motions into seismic risk evaluations, particularly for structures near fault zones.</p>

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Simulation study of the effects of fault zone on seismic translational and rotational motions

  • 期刊论文

  • 发表日期：

    2025年7月14日

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  • Wei Li,
  • Yun Wang,
  • Chang Chen,
  • Lixia Sun,
  • Yongxiang Wei,
  • Chunqi Liao

摘要

Low-velocity fault zones, predominantly located in the shallow crust (0–5 km depth), amplify localized earthquake-triggered ground shaking, thereby exacerbating the vulnerability of surface structures. Understanding the influences of fault zones on seismic wave propagation, including their effects on both translational and rotational ground motions, is necessary for seismic hazard assessment. We first establish a 2D model based on the Binhai fault zone in the Taiwan Strait and a Hualien MW 6.1 earthquake and then use the staggered-grid finite difference method to simulate seismic wavefields of translational (X, Z) and rotational Y (Ry) components in models with and without a normal fault zone. By evaluating amplitude and spectral characteristics of ground motion across observation positions along the fault, we investigate the responses of translational and rotational component motions to the fault zone. Results demonstrate spatially heterogeneous amplification and attenuation effects and differential responses between seismic rotational and translational motions: (i) The fault zone amplifies ground motions asymmetrically on its northwestern (NW) and southeastern (SE) sides (up to 300% and 100% amplification, respectively), while attenuating amplitudes (40–70% reduction) in its overlying central region. (ii) Near the fault (≤ 10 km), Ry-component amplitudes exceed translational components by 20–80%, but this enhancement diminishes, becoming 20–120% weaker at farther distances (~ 10–30 km). (iii) High-frequency Ry signals exhibit stronger amplification and weaker attenuation compared to translational components, highlighting frequency-dependent fault-zone dynamics. These findings underscore the necessity of incorporating rotational ground motions into seismic risk evaluations, particularly for structures near fault zones.