Recent Improvements in the Analysis of Surface Wave Observations
Recent Improvements in the Analysis of Surface Wave Observations
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DOI：
10.1111/j.1365-246x.1969.tb00246.x
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发表时间：
1969-05
影响因子：
2.8
通讯作者：
M. Landisman;A. Dziewoński;Yasuo Satô
中科院分区：
文献类型：
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作者：
M. Landisman;A. Dziewoński;Yasuo Satô
摘要 地震瞬态的移动窗口分析可用于测量多模传播记录中的群速度。它将普通时间序列（幅度与时间）转换为速度与对数周期平面上的二维分贝显示。可以针对观察到的每种模式来研究激励和衰减的影响。将这种分析方法应用于相互正交探测器的记录，可以测量横向折射，将拉夫波与瑞利波分开，并有望用于识别基本模式和更高模式。在记录地点接收到的模式可以通过时变滤波器与观察到的复合信号分离。如果这些滤波器基于从移动窗口分析推断的色散，则可以获得信噪比的显着改进。描述了频域中的滤波，并将其与时域中的滤波进行了比较。小事件的站间相速度测量可以扩展到以前仅针对重大事件的波列大圆通道测量的周期。为了实现这些改进，（a）应使用移动窗口分析来测量频散，（b）应使用基于观测到的频散的频域时变滤波器从两个台站的记录中提取所需的模式，以及（c）应根据这些滤波后的地震图的加窗互相关图来计算相速度。从匹配记录计算出的站间互相关图可以被认为是站间弹性介质对空间和时间上的脉冲的响应的近似表示，该脉冲施加在第一站处并由第二站处的无畸变位移计记录。因此，可以通过互相关图的移动窗口分析来评估站间群速度，而不需要对观测到的相速度曲线进行数值微分。
Summary Moving window analysis of seismic transients can be used to measure group velocity in recordings of multi-mode propagation. It converts an ordinary time series (amplitude vs time) into a two-dimensional display of decibels on a velocity vs log period plane. The effects of excitation and attenuation may be studied for each of the modes observed. Application of this method of analysis to the recordings of mutually orthogonal detectors permits the measurement of lateral refraction, the separation of Love waves from Rayleigh waves and promises to be useful in the identification of the fundamental and higher modes. The modes received at the recording site may be separated from the observed composite signal by means of time-variable filters. A significant improvement in signal-to-noise can be obtained if these filters are based upon the dispersion inferred from moving window analysis. Filtration in the frequency domain is described and compared to filtration in the time domain. Inter-station phase velocity measurements from small events may be extended to periods previously measured only for great circle passages of wave trains from major events. In order to achieve these improvements (a) moving window analysis should be used to measure the dispersion, (b) a frequency-domain time-variable filter based upon the observed dispersion should be used to extract the desired mode from the records of both stations, and (c) the phase velocity should be calculated from the windowed crosscorrelogram of these filtered seismograms. The inter-station cross-correlogram computed from matched recordings may be considered an approximate representation of the response of the inter-station elastic medium to an impulse in space and time, applied at the first station and recorded by a distorsionless displacement metre at the second station. Inter-station group velocity thus can be evaluated by moving window analysis of the cross-correlogram, without resort to numerical differentiation of the observed phase velocity curve.