地质学
瑞利波
地震学
地震噪声
表面波
环境噪声级
噪音(视频)
相速度
地貌学
物理
光学
计算机科学
图像(数学)
人工智能
声音(地理)
作者
Tongwei Qin,Laiyu Lu,Zhifeng Ding,Xuanzheng Feng,Youyuan Zhang
摘要
The 3D S wave velocity of shallow structures, especially the quaternary sediments at 0–1 km near the surface, is an important issue of concern in urban planning and construction for seismic hazard assessment and disaster mitigation. Due to the facility and less dependence on the site environment, noise-based technique is an ideal way to acquire the fine structure of urban sedimentary basin. Based on the dense array composed of more than 900 stations deployed in Tongzhou at a local scale of 20 × 40 km2, we prove that the lateral variation of the phase velocity of multimode surface waves can be estimated directly with sufficient accuracy by beamforming seismic noise with moving subarrays. Rayleigh wave phase velocity maps, at frequencies between 0.3 and 2.5 Hz for the fundamental mode as well as 0.8 and 3.0 Hz for the first overtone, are obtained. The 3D S wave velocity model at 0–1-km depth with lateral resolution of 1 km is then established by inverting phase velocity maps of the two modes. The sediment thickness is delineated by the impedance interface given by microtremor H/V (horizontal-to-vertical) spectral ratio. The proposed model is in good agreement with the distribution of tectonic units. The sediment thickness of Daxing high and two sags around Gantang and Xiadian are, respectively, 100–400 and 400–600 m, which correlates well with the 1 km/s isosurface of S wave velocity. The model presents some evidence on the extension of Daxing fault along NE direction.
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