The utility of acoustic-to-seismic coupling systems for land mine detection has been clearly established with potential as either a primary or confirmation sensor system. They can detect very low metal content mines that are difficult for ground-penetrating radar detection. For most applications, only the magnitude of the surface velocity is used to construct recognition algorithms. Recently, we introduced phase-based features in the classification scheme, significantly lowering false alarm rates at given detection probabilities. In this paper we introduce modeling equations that explain the phase features. We also describe the image processing techniques applied to velocity data collected in the time domain.