Acoustic and seismic modalities for unattended ground sensors

The use of acoustic and seismic modalities in unattended ground sensor systems has been an active area of research. However, a thorough study of the advantages and complementary aspects of the two modalities has not heretofore been considered. This paper provides a detailed description of both acoustic and seismic methods for unattended ground sensors. We discuss acoustic and seismic phenomenology; source mechanisms, propagation paths, attenuation, and sensing. These phenomena significantly impact the detection, identification, and localization objectives of unattended ground sensors. As such, certain applications will benefit from exploiting acoustic ground sensing, seismic ground sensing, or in some cases, both. A methodology is presented for selecting the preferred modality (acoustic and/or seismic) for a particular applications. It is shown that the preferred modality significantly impacts the architecture of the ground sensor system. Important system architecture criteria such as transducer selection, data acquisition bandwidth, array geometry, and communications requirements are considered in this paper. Furthermore, the effects of seismo-acoustic and acousto-seismic interactions are addressed. It is shown that acoustic transducers may respond to seismic excitation, and seismic transducers often respond to acoustic excitation. In some instances, this dual-modality is of benefit. We also provide recommendations for minimizing seismic/acoustic cross talk for applications requiring independent seismic or acoustic modes.