The effectiveness of sensors to identify, locate and characterize a facility depends on several factors, namely, the types of equipment being monitored, the location of the equipment, the mounting of the equipment to the structure, the physical configuration of the facility, the surrounding propagating media, and the effects of natural and cultural background noise. We have developed electromagnetic, seismic, and acoustic source and propagation models to theoretically investigate these issues for facility models in realistic geological media. Source models for various machine types have been developed along with an electromechanical system parameter database. The model produces expected time-varying currents on the power lines which generate electromagnetic fields observed by EM sensors. The time-varying torque function defined in the model gives the expected force time function for the seismic and acoustic source. Propagation models have been developed, using 2D seismic, acoustic and electromagnetic finite- difference techniques, for propagating the fields through the structure and earth medium to far-field sensors. In this research, we are also investigating methods for fusing EM and seismic/acoustic signatures for more complete characterization of the operational elements in a facility. The products of the effort are enhanced key components of a forward modeling system incorporating a CAD-style interface for specifying facility models, equipment locations and surrounding media. We envision the system as a tool to estimate detection ranges and optimal sensor placement for monitoring a facility.