<title>Problems in seismic detection and tracking</title>

One can detect and track vehicles and personnel using a three-component seismic velocity transducer. Persons or vehicles moving over ground generate a succession of impacts; these soil disturbances propagate away from the source as seismic waves. Because the soil is an elastic medium both vertical and longitudinal waves propagate, diminishing in intensity as R<SUP>-2</SUP>. Furthermore because the surface of the soil is the boundary of an elastic space, a Rayleigh surface wave is also generated, diminishing in intensity as R<SUP>-1</SUP>. This surface wave is a vector wave that can be used to track the source. In addition to the classic model of surface waves on an elastic half space we discuss special features of seismic measurements. Among these are: contamination of the seismic signal by local acoustic waves, the excess non-geometric attenuation of the seismic signal, the influence of reflections from layered soil in tracking personnel, and finally a method of ranging using the periodic impact signature of vehicles.