Abstract Soil dynamic parameters such as shear wave velocity and damping ratio are of major interest in earthquake engineering. While the shear wave velocity, directly linked to the shear modulus, can be determined by a number of laboratory and in-situ tests with satisfying accuracy the damping ratio is much more difficult to obtain. Especially the results of in-situ experiments show often large variations. This is in general due to the troublesome determination of precise signal amplitudes whether in time or frequency domain related with these techniques. The paper presented comes back to a relationship between attenuation and velocity dispersion of body waves which replaces the measurement of the amplitude characteristics of seismic signals by a frequency dependent velocity function. The implementation of this method has previously shown to be difficult because of the very small levels of dispersion observed in seismic data. Our approach aims to overcome the problem by applying a multi-channel spectral analysis which is widely used in surface wave testing to calculate a velocity dispersion. Multi-channel measurements have shown to be more tolerant to erroneous phase characteristics of single seismic traces than the more common two station measurements. The velocity dispersion curve is extracted from a phase velocity–frequency spectrum and the damping ratio is calculated by fitting a theoretical dispersion curve to the extracted curve. The method is demonstrated on correlated data of a seismic downhole test performed using a S-wave vibrator source. The obtained results show a reasonable agreement with damping ratios found in the literature for similar soils.

中文翻译：

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地震井下数据多道谱分析确定阻尼比

摘要 土体动力参数如剪切波速度和阻尼比是地震工程中的主要研究对象。虽然与剪切模量直接相关的剪切波速度可以通过许多实验室和现场测试以令人满意的精度确定，但阻尼比更难获得。尤其是原位实验的结果往往显示出很大的变化。这通常是由于在与这些技术相关的时域或频域中很难确定精确的信号幅度。提交的论文回到了体波的衰减和速度色散之间的关系，该关系用频率相关的速度函数代替了对地震信号幅度特性的测量。由于在地震数据中观察到的色散水平非常小，因此这种方法的实施以前已经证明是困难的。我们的方法旨在通过应用广泛用于表面波测试的多通道光谱分析来计算速度色散来克服该问题。与更常见的两个台站测量相比，多通道测量已显示出对单个地震道的错误相位特征的容忍度更高。速度色散曲线是从相速度-频率谱中提取的，阻尼比是通过将理论色散曲线拟合到提取的曲线来计算的。该方法在使用 S 波振动器源执行的地震井下测试的相关数据上得到证明。