Effects of Environment on Seismic Intrusion Detector Performance

Improved guidance manuals for planning the deployment and emplacement of seismic intrusion detectors SIDs are needed to optimize the use of these devices for battlefield surveillance. The development of these Military Geographic Intelligence MGI products requires a detailed understanding of the operating principles of the detector coupled with an equally detailed understanding of the interactions of the sensor propagation mode with the operational environment. This report presents the results of a preliminary analysis of data collected in a wide range of environments at 22 sites in Panama, 10 sites in Puerto Rico, 6 sites near Yuma Proving Ground, Arizona, and 9 sites near Ft. Huachuca, Arizona. Multiple regression techniques were used to determine the terrain factors that could be correlated with the seismic responses resulting from a man walking or a controlled source drop hammer that simulated the signature resulting from a footstep. The measure of seismic response was peak particle velocity as a function of distance from the source. The terrain factors that correlated best with peak particle velocity were the thickness of the first refraction layer, cone index of the 0- to 15-cm soil layer, dry density of surface soil and first soil layer, water content of surface soil and first soil layer, compression wave velocity, Rayleigh wave velocity, and grain-size distribution. An empirical equation was developed to predict peak particle velocity versus distance as a function of the terrain factors.