Improving SASW Dispersion Measurements with Source Correlation and Receiver Arrays

摘要[9901225]PI: James a . Bay研究所：犹他州立大学“利用源相关和接收器阵列改进表面波谱分析（SASW）方法”表面波谱分析（SASW）方法是一种用于确定浅层土壤和岩石沉积物工程性质的地震技术。它涉及到在地面产生地震波，并通过放置在地面上的许多接收器监测地震波的运动。在SASW测试中经常遇到的一个困难是，来自其他来源的地震能量，如交通、工业设施甚至树木中的风，也要由接收器测量。这种不必要的地震能量或噪音会污染SASW测量结果，并可能导致错误的结果。本研究旨在探讨两种减小噪声对SASW测量影响的方法。这些方法可以提高SASW测量的质量。第一种建议的方法是使用源相关性。这包括测量SASW源施加到地面的力，并将该力函数与每个接收器上测量到的信号相关联。通过重复测量并平均相关函数，可以降低SASW测量中的噪声水平。使用源相关性的另一个好处是SASW测试，它将允许对实验结果的质量进行统计确定。使用这种方法的另一个好处是，通过源相关性，在激励函数和每个接收器之间计算的相干函数将准确地量化每个接收器处的噪声频谱分布。利用这些信息，可以统计地确定相干水平、平均次数和被测相位置信区间之间的关系。有了这种关系，执行SASW测试的操作人员将能够根据相干水平确定需要多少个平均值才能达到所需的测量精度。第二种方法是减少噪声的影响，使用接收器阵列来最小化噪声对表面波色散测量的影响。接收器阵列是接收器数量串联的几何分布，因此来自所有传感器的信号被求和。几十年来，勘探地球物理学家一直使用接收器阵列来最小化深反射测量中表面波（地球物理学家称之为地滚）的影响。通过使用传感器的不同空间分布，可以设计接收器阵列，选择性地测量表面波，并消除从源位置以外的点发出的噪声。该研究将提高sw现场测量的质量。此外，准确量化SASW测量中的噪声级将为未来研究评估最终SASW结果的分辨率提供有价值的工具。

Abstract 9901225 PI: James A. Bay Institution: Utah State University "Improving SASW Dispersion Measurements with Source Correlation and Receiver Arrays" The Spectral-Analysis-of Surface-Waves (SASW) method is a seismic technique for determining engineering properties of shallow soil and rock deposits. It involves generating seismic waves at the ground surface and monitoring the motions of those waves with a number of receivers positioned on the ground surface. One difficulty that is often encountered in SASW testing is that seismic energy from other sources, such as traffic, industrial facilities and even wind in trees is also measured by the receivers. This unwanted seismic energy, or noise, contaminates SASW measurements and can lead to erroneous results. This proposed research is to investigate two approaches to minimize the influence of noise on SASW measurements. These methods should improve the quality of SASW measurements. The first proposed approach is to use source correlation. This involves measuring the force applied to the ground by the SASW source, and correlating that forcing function with the signal measured at each receiver. By repeating the measurement and averaging the correlated functions, the noise level in the SASW measurement will be decreased. An additional benefit of using source correlation is SASW testing is that it will allow a statistical determination of the quality of experimental results. An added benefit to using this approach is that with source correlation, coherence functions calculated between the excitation function and each receiver will accurately quantify the spectral distribution of noise at each receiver. With this information, the relationship between coherence level, number of averages, and the confidence interval of the measured phase can be determined statistically. With this relationship an operator performing SASW testing will be able to determine how many averages will be required to achieve a desired measurement accuracy based upon the coherence level. The second approach is to reducing the influence of noise the use of receiver arrays to minimize the effects of noise on surface wave dispersion measurements. A receiver array is a geometric distribution of number of receivers connected in series, so that signals from all the sensors are summed. For decades, exploration geophysicists have used receiver arrays to minimize the effects of surface waves (which geophysicists refer to as ground roll) in deep reflection surveys. By using different spatial distributions of the sensors, receiver arrays can be designed that will selectively measure the surface waves and eliminate noise emanating from points other than the source location. This research will result in higher quality SASW field measurements. In addition, accurately quantifying noise levels in SASW measurements will provide a valuable tool for future research in assessing the resolution of final SASW results.