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<p>Sedimentary basins have long been recognised as amplifiers of earthquake ground motions, contributing to severe damage in events like the 1985 Mexico City, 1994 Northridge, and 1995 Kobe earthquakes. Amplification arises from impedance contrasts between sediment layers, which can trap seismic energy during an earthquake. This energy leads to multiple reflections, refractions, and long-period reverberations that significantly influence the resulting ground motion. The present study focuses on analysing the effect of the geometry of sedimentary basins on seismic wave propagation and amplification. We have used a two-dimensional spectral element simulation to model the problem. The numerical models have a half-elastic medium considering P-SV waves and utilise idealised basin shapes to examine the effects of basin geometry and material properties. Here we investigate the time domain response, frequency domain response, and velocity response spectra of the ground motions simulated at various basin cross sections, such as rectangular, trapezoidal, parabolic and foreland basins. Also, the amplification of ground motions is analysed with respect to the depth of the basin, distance from the epicentre, and frequency for the different basin geometry models. The results demonstrated that the geometry of the basin has a significant impact on seismic wave amplification, both in terms of the amplitude and the duration of the waves. Also, to understand the seismic wavefield generated at a real-world basin site, ground motions are simulated at the Indo-Gangetic basin by considering the best-known material properties and basin structure. The results indicate that the long-period surface waves have relatively more amplitude and duration compared to the stations outside the basin. Additionally, it has been noted that basin stations situated further from the edges of the basin exhibit heightened surface wave activity in the 2D simulation. This phenomenon can be ascribed to the pronounced basin-edge effect evident in the 2D simulation.</p>

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Effect of basin geometry in seismic wave amplification

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • K P Sreejaya,
  • Surya Narayan Behera,
  • S T G Raghukanth

摘要

Sedimentary basins have long been recognised as amplifiers of earthquake ground motions, contributing to severe damage in events like the 1985 Mexico City, 1994 Northridge, and 1995 Kobe earthquakes. Amplification arises from impedance contrasts between sediment layers, which can trap seismic energy during an earthquake. This energy leads to multiple reflections, refractions, and long-period reverberations that significantly influence the resulting ground motion. The present study focuses on analysing the effect of the geometry of sedimentary basins on seismic wave propagation and amplification. We have used a two-dimensional spectral element simulation to model the problem. The numerical models have a half-elastic medium considering P-SV waves and utilise idealised basin shapes to examine the effects of basin geometry and material properties. Here we investigate the time domain response, frequency domain response, and velocity response spectra of the ground motions simulated at various basin cross sections, such as rectangular, trapezoidal, parabolic and foreland basins. Also, the amplification of ground motions is analysed with respect to the depth of the basin, distance from the epicentre, and frequency for the different basin geometry models. The results demonstrated that the geometry of the basin has a significant impact on seismic wave amplification, both in terms of the amplitude and the duration of the waves. Also, to understand the seismic wavefield generated at a real-world basin site, ground motions are simulated at the Indo-Gangetic basin by considering the best-known material properties and basin structure. The results indicate that the long-period surface waves have relatively more amplitude and duration compared to the stations outside the basin. Additionally, it has been noted that basin stations situated further from the edges of the basin exhibit heightened surface wave activity in the 2D simulation. This phenomenon can be ascribed to the pronounced basin-edge effect evident in the 2D simulation.