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<p>Existing research indicates that seismic responses in deep soft seabeds are affected by fluid–solid coupling, seabed micro-topography, soil spatial heterogeneity, and nonlinearity. To address these complexities, this study develops an integrated nonlinear seismic response analysis for a cross-strait transect. The method comprehensively incorporates the strait basin geometry, detailed seabed microtopographic features, spatially varying soil properties (including S and P wave velocity structures), a nonuniform mesh layout of the transect, and appropriate artificial boundary conditions. Particular emphasis is placed on the seawater–seabed interaction, simulated via a weak coupling algorithm for fluid–solid interaction, and on the soil’s nonlinear hysteretic behavior. Numerical simulations, conducted without considering seawater effects, reveal three key findings. First, bedrock motion components near the seabed fundamental frequency show enhanced upward propagation through the soil deposits. Second, seabed microtopography exerts a more pronounced influence on vertical seafloor motions than on horizontal components. Third, a resonance-like phenomenon occurs near 2 Hz for both horizontal and vertical motion components. The complex interplay of seismic wave reflection, refraction, and interference within heterogeneous deposits generates intricate, strongly coupled amplification patterns. However, when seawater–seabed coupling is considered, significant suppression of seafloor peak accelerations is observed, especially in deepwater regions. Vertical motions exhibit more pronounced suppression within specific narrow frequency bands compared to horizontal motions. The seabed seismic responses exhibit significant higher-frequency suppression (near 4–5 Hz) and low frequency amplification (&lt; 0.5 Hz), while the resonance-like responses near 2.0 Hz for both horizontal and vertical components are diminished. Crucially, the degree of suppression or amplification of these resonance-like responses correlates positively with the seabed bedrock motion intensity.</p>

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2D nonlinear seismic response characteristics of a cross-strait seabed site considering seawater-seabed coupling effects

  • 期刊论文

  • 发表日期：

    2026年5月20日

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  • Guoxing Chen,
  • Zhijie Jiang,
  • Yanzhen Wang,
  • Kai Zhao,
  • Weiyun Chen,
  • Charng-Hsein Juang

摘要

Existing research indicates that seismic responses in deep soft seabeds are affected by fluid–solid coupling, seabed micro-topography, soil spatial heterogeneity, and nonlinearity. To address these complexities, this study develops an integrated nonlinear seismic response analysis for a cross-strait transect. The method comprehensively incorporates the strait basin geometry, detailed seabed microtopographic features, spatially varying soil properties (including S and P wave velocity structures), a nonuniform mesh layout of the transect, and appropriate artificial boundary conditions. Particular emphasis is placed on the seawater–seabed interaction, simulated via a weak coupling algorithm for fluid–solid interaction, and on the soil’s nonlinear hysteretic behavior. Numerical simulations, conducted without considering seawater effects, reveal three key findings. First, bedrock motion components near the seabed fundamental frequency show enhanced upward propagation through the soil deposits. Second, seabed microtopography exerts a more pronounced influence on vertical seafloor motions than on horizontal components. Third, a resonance-like phenomenon occurs near 2 Hz for both horizontal and vertical motion components. The complex interplay of seismic wave reflection, refraction, and interference within heterogeneous deposits generates intricate, strongly coupled amplification patterns. However, when seawater–seabed coupling is considered, significant suppression of seafloor peak accelerations is observed, especially in deepwater regions. Vertical motions exhibit more pronounced suppression within specific narrow frequency bands compared to horizontal motions. The seabed seismic responses exhibit significant higher-frequency suppression (near 4–5 Hz) and low frequency amplification (< 0.5 Hz), while the resonance-like responses near 2.0 Hz for both horizontal and vertical components are diminished. Crucially, the degree of suppression or amplification of these resonance-like responses correlates positively with the seabed bedrock motion intensity.