Measurement and localization of interface wave reflections from a buried target

Abstract

It is demonstrated that seismic interface waves on the surface of a natural beach can be used to identify the position of a buried object. For this experiment, the waves were created with a sediment-coupling transducer and received on a three-element horizontal line array of triaxial geophones. The source and its coupling to the medium provided a high degree of signal repeatability, which was useful in improving signal-to-noise ratio. Reception of all three directions of particle velocity made it possible to augment conventional beamforming techniques with polarization filters to enhance interface-wave components. Reverberation in the beach was found to be large, though, and coherent background subtraction was required to isolate the component of the sound field reflected by the target. Propagation loss measurements provided comparisons of reflected signal power with predictions made previously, and the two were found to agree closely.

Environmental factors that impact the performance of a seismic landmine detection system

“…The peaks of this waveform have been clipped in the figure in order to display both wave types in a single graph. This speed is consistent with the other reported observations of Rayleigh waves in both sand and hard soil [7,9]. The coda associated with the Rayleigh wave arrival is longer and more complex in the field data than in the laboratory because of the variety of surface and subsurface inhomogeneities at the field site.…”

“…Two distinct arrivals are observed at each site. The first of these (any apparent earlier arrivals are caused by noise-induced processing artifacts) arrives with a group velocity of 170 m/s to 183 m/s, which is consistent with observed P-wave velocities [8] and with observations of leaky surface waves [9] at similar sites. The series of small arrivals immediately following the first arrival may account for the latter observation, although both wave types may not exist with measurable amplitude in the data.…”

On Some DOA Algorithms for Tri-axial Geophone

“…The other methods, also partially based on the correlation analysis [13], [5], [6], seem to be worse than methods proposed in this paper although the direct comparison is impossible because of the lack of appropriate results for comparison and the lack of detailed descriptions of the methods presented in the literature.…”

“…To effectively apply equations (6,7,8) in the direction finding problem we further suppose the noise components have sufficiently small variances and their mean values are equal to zero. Otherwise the detected signals have to be properly smoothed and denoised.…”

“…Various methods have been developed to find DOA with the use of tri-axial geophone, though two of them seem to be the most commonly reported in the literature of the field. The first class of methods utilizes the properties of the covariance matrix (CMA -covariance matrix analysis) [5], [6], [7], [8], [9], [10], [11], [12], while the second class of methods exploits the properties of seismic waves, especially the properties of the Rayleigh surface plane wave [13], [7], [8], [10]. In this paper we propose a method that can be considered as an extension of those proposed in [7], [8], [14].…”