This study presents broadband ground motions for the Indo-Gangetic basin, a large sedimentary basin in India, for potential future great (Mw 8.5) Himalayan earthquakes. We use a recently developed 3D earth structure model of the basin as an input to simulate low-frequency ground motion (0–0.5 Hz). These ground motions are further combined with high-frequency scattering waveforms by using a hybrid approach, thus yielding broadband ground motions (0–10 Hz). We calibrate the 3D model and scattering parameters by comparing the simulated ground motions against available recorded data for two past earthquakes in Himalaya. Our approach accounts for the physics of interaction between the scattered seismic waves with deep basin sediments. Our results indicate that the ground motion intensities exhibit frequency-dependent amplification at various basin depths. We also observe that in the event of a great earthquake, the ground motion intensities are larger at deep basin sites near the source and exhibit an attenuating trend over distance similar to the ground motion models. The extreme ground motion simulations performed in our study reveal that the national building codes may not provide safe recommendations at deep basin sites, especially in the near field region. The period-dependent vertical-to-horizontal spectral ratio deviates from the code-recommended constant 2/3 at least up to 6 s at these sites.

这项研究提出了印度-恒河盆地（印度的一个大型沉积盆地）的宽带地面运动，以应对未来可能发生的喜马拉雅大地震（Mw 8.5）。我们使用盆地最近开发的3D地球结构模型作为模拟低频地面运动（0–0.5 Hz）的输入。通过使用混合方法，将这些地面运动与高频散射波形进一步结合，从而产生宽带地面运动（0-10 Hz）。我们通过将模拟的地面运动与喜马拉雅山两次地震的可用记录数据进行比较，来校准3D模型和散射参数。我们的方法考虑了分散的地震波与深盆地沉积物相互作用的物理原理。我们的结果表明，在不同的盆地深度，地震动强度表现出频率相关的放大作用。我们还观察到，在发生大地震的情况下，震源附近较深盆地部位的地震动强度较大，并且在距离上表现出类似于地震动模型的衰减趋势。在我们的研究中进行的极端地面运动模拟表明，国家建筑法规可能无法在深流域现场提供安全建议，尤其是在近场区域。在这些位置，与周期有关的垂直/水平光谱比至少在6 s内偏离代码建议的常数2/3。在震源附近的深盆地部位，地震动强度较大，并且在距离上表现出类似于地震动模型的衰减趋势。在我们的研究中进行的极端地面运动模拟表明，国家建筑法规可能无法在深流域现场提供安全建议，尤其是在近场区域。在这些位置，与周期有关的垂直/水平光谱比至少在6 s内偏离代码建议的常数2/3。在震源附近的深盆地部位，地震动强度较大，并且在距离上表现出类似于地震动模型的衰减趋势。在我们的研究中进行的极端地面运动模拟表明，国家建筑法规可能无法在深流域现场提供安全建议，尤其是在近场区域。在这些位置，与周期有关的垂直/水平光谱比至少在6 s内偏离代码建议的常数2/3。