Detection Of Near-Surface Voids Using Surface Wave

Ground roll is displayed, on an uncorrelated field record obtained using a monotonic<br>sweep, in increasing or decreasing order of frequency with each frequency well separated from<br>all others. Phase velocity and attenuation characteristics of each frequency contain the average<br>elastic property of near-surface materials down to approximately half the wavelength.<br>Uncorrelated field record, therefore, by itself can be associated with a two-dimensional display<br>of the change in near-surface elastic property. Through the redundancy in data acquisition and<br>a simple data processing step, the uncorrelated field records can be transformed into a stacked<br>section that can be correlated directly to image of the change in elastic property of near-surface<br>materials with respect to a certain reference location. This method can be effectively used to<br>detect near-surface anomalies of various kinds.