Single-axis geophones have been used in Unattended Ground Sensor applications to detect personnel and vehicles. These devices are unable to determine the direction of arrival of the signal. However, a seismic wave is a complex process whose direction can be determined by sensing the full 3-dimensional motion of the soil. The objective of this SBIR effort is to develop and implement algorithms and code capable of determining the direction of a seismic source using a single tri-axial geophone. This capability can lead to compact tactical seismic sensors able to detect and track ground targets. We propose an algorithm based on an analysis of the polarity of the Rayleigh wave. In the scenarios of interest, with sensors placed on or near the surface and target ranges of 100 m or less the bulk of the arriving seismic energy will be in the form of a Rayleigh wave. Results obtained to date show the potential utility of this technique. They also show that the results can vary significantly from location to location. A significant contribution of this project will be a better understanding of the applicability and limitations of this technique and the development of adaptive algorithms that can produce more consistent results.
Keywords: Seismic Sensors, Tri-Axial Geophone, Unattended Ground Sensor, Tactical Ugs
