Amplification of Seismic Waves in the Central Indo-Gangetic Basin, India
Amplification of Seismic Waves in the Central Indo-Gangetic Basin, India
复制标题
DOI：
10.1785/0120100327
复制
发表时间：
2011-10
影响因子：
3
通讯作者：
D. Srinagesh;S. K. Singh;R. Chadha;A. Paul;G. Suresh;M. Ordaz;R. S. Dattatrayam
中科院分区：
文献类型：
--
作者：
D. Srinagesh;S. K. Singh;R. Chadha;A. Paul;G. Suresh;M. Ordaz;R. S. Dattatrayam
印度-恒河盆地虽然毗邻喜马拉雅大地震（M ≥6）的破裂区，但对该地区地震波放大的定量研究还很缺乏。为了获得放大的初步估计，两年来，我们运行了一个由10个宽频带地震仪组成的阵列，这些地震仪沿南北方向穿过印度-恒河盆地中部。利用软场地和硬参考场地的浅源地震记录，计算了标准谱比（SSR s）。在喜马拉雅山麓附近的SSR卫星上，沉积物厚度为1.4km，显示出基频为0.13Hz的宽带放大。该频率下的放大率在20和60之间变化。随着沉积物厚度的减小，基频向南增加，在最南端变为100：8Hz。在所有8个软站点，基频放大率均超过10。根据合理的震源和衰减模型，应用随机振动理论，计算表明，在距震中100 km的山麓软土地基上，地面峰值加速度和地面峰值速度将分别放大2 - 4倍和6 - 12倍，所有结果都符合地基的线性特性。然而，我们的研究结果为非线性行为的研究提供了基本的基础。2在线资料：放大率、光谱比和加速度谱的补充图。
Abstract Although the Indo-Gangetic basin is adjacent to rupture areas of largeHimalayan earthquakes (M ≥6), a quantitative study of the amplification of seismicwaves in the region is still lacking. To obtain a first estimate of the amplification, fortwo years we operated an array of 10 broadband seismographs that crossed the centralIndo-Gangetic basin in a north–south direction. Using earthquake recordings ofshallow earthquakes at soft sites and hard reference sites, we computed standard spec-tralratios( SSR s). SSR satsitesneartheHimalayanfoothills,wherethesedimentthick-ness is ∼4 km, reveal a broadband amplification with a fundamental frequency of0.13 Hz. The amplification at this frequency varies between 20 and 60. The funda-mental frequency increases to the south as the thickness of the sediments decreases,becoming ∼0:8 Hz at the southernmost site. The amplification at the fundamentalfrequencies exceeds 10 at all eight soft sites. Calculations based on reasonable earth-quake source and attenuation models and application of random vibration theorysuggest that peak ground acceleration and peak ground velocity at soft sites nearthe foothills, located 100 km from the epicenter, would be amplified by a factorof2–4and6–12,respectively.All ourresultsassumelinear behaviorofthesediments.Although this assumption would not be valid during intense motions resultingfrom large earthquakes, our results, nevertheless, provide basic building block forincorporating nonlinear behavior.Online Material: Supplementary figures of amplification, spectral ratio, andacceleration spectra.Introduction