Analysis of three-component ambient vibration array measurements
Analysis of three-component ambient vibration array measurements
复制标题
三分量环境振动阵列测量分析
DOI：
10.1111/j.1365-246x.2007.03625.x
复制
发表时间：
2008
影响因子：
2.8
通讯作者：
H. Havenith
中科院分区：
文献类型：
--
作者：
D. Fäh;G. Stamm;H. Havenith
总结
合成和观察到的环境振动阵列数据进行了分析，使用高分辨率波束形成。除了一个经典的垂直分量的分析，本文提出了来自处理水平分量的结果。我们分析相速度的基本和更高的模式瑞利波和爱波，和粒子运动（椭圆）检索的H/V谱比。结合反演与遗传算法和选择可能的模型参数的策略，使我们能够定义解释数据的结构模型。从具有一层或两层沉积物的简单模型的合成数据得出的结果表明，在大多数情况下，必须将沉积物层的数量减少到几个沉积层才能找到原始结构。一般来说，减少软沉积层的数量在反演过程中与遗传算法导致一类模型是不太光滑。它们在沉积物和基岩之间具有更强的阻抗对比。
将Love和Rayleigh波频散曲线与基模Rayleigh波的椭圆率相结合具有一定的优越性。与仅从瑞利波相速度曲线获得的结构模型相比，散射减小。通过添加来自Love波的信息，可以排除某些结构。约束反演结果的另一种可能性是包括补充地质或钻孔信息。分析径向分量还可以提供在垂直分量上看不到的模式的瑞利波频散曲线段。最后，利用椭圆率信息，使我们能够限制软沉积物的总深度。
对于真实的网站，相当大的变化，在测得的相速度曲线观察。这来自阵列内结构或地震源的横向变化。通过结合Love和Rayleigh波信息约束反演可以帮助减少此类问题。瑞利波频散曲线表现出相当大的散射的频带通常由Love波更好地分辨。
来自水平分量的信息可用于正确地将模式编号分配给不同的相速度曲线段，特别是当两个模式似乎在密切点处合并时。这种模式的合并通常是观察到的瑞利波，因此可以部分解决，如果额外的信息从洛夫波和水平分量的瑞利波被认为是。无论何时，当一个场地在顶层以下出现速度反演时，Love波数据显然有助于更好地约束解。
SUMMARY
Both synthetic and observed ambient vibration array data are analysed using high-resolution beam-forming. In addition to a classical analysis of the vertical component, this paper presents results derived from processing horizontal components. We analyse phase velocities of fundamental and higher mode Rayleigh and Love waves, and particle motions (ellipticity) retrieved from H/V spectral ratios. A combined inversion with a genetic algorithm and a strategy for selecting possible model parameters allow us to define structural models explaining the data. The results from synthetic data for simple models with one or two layers of sediments suggest that, in most cases, the number of layers has to be reduced to a few sediment strata to find the original structure. Generally, reducing the number of soft-sediment layers in the inversion process with genetic algorithms leads to a class of models that are less smooth. They have a stronger impedance contrast between sediments and bedrock.
Combining Love and Rayleigh wave dispersion curves with the ellipticity of the fundamental mode Rayleigh waves has some advantages. Scatter is reduced when compared to using structural models obtained only from Rayleigh wave phase velocity curves. By adding information from Love waves some structures can be excluded. Another possibility for constraining inversion results is to include supplementary geological or borehole information. Analysing radial components also can provide segments of Rayleigh wave dispersion curves for modes not seen on the vertical component. Finally, using ellipticity information allows us to confine the total depth of the soft sediments.
For real sites, considerable variability in the measured phase velocity curves is observed. This comes from lateral changes in the structure or seismic sources within the array. Constraining the inversion by combining Love and Rayleigh wave information can help reduce such problems. Frequency bands in which the Rayleigh wave dispersion curves show considerable scatter are often better resolved by Love waves.
Information from the horizontal component can be used to correctly assign the mode number to the different phase–velocity curve segments, especially when two modes seem to merge at osculation points. Such merging of modes is usually observed for Rayleigh waves and thus can be partly solved if additional information from the Love waves and the horizontal component of Rayleigh waves is considered. Whenever a site presents a velocity inversion below the top layer, Love wave data clearly helps to better constrain the solution.