Recent success in using a laser Doppler vibrometer (LDV) based acoustic-to-seismic (A/S) landmine detection [Sabatier, J. M. and Xiang, N. IEEE Trans. Geoscience and Remote Sensing 39, 2001, pp.1146-1154.; Xiang, N. and Sabatier, J. M., J. Acoust. Soc. Am. 113, 2003, pp. 1333-1341] and a ground penetrating synthetic aperture radar (GPSAR) [Bradley et al. Proc. SPIE, 4038, pp.1001-1007, 2000] suggested a novel configuration of fused sensors comprised of a LDV-based A/S detection sensor and a GPSAR. Extensive field experiments revealed that these two technologies can be considered 'orthogonal'. When used in concert, a fused configuration may significantly improve the probability of detection and reduce the false alarm rate. They function best against different types of landmines under different burial conditions because they exploit disparate phenomena to detect mines. In order to better understand the fused detection ability, a co-located field experiment has been conducted using both a LDV-based A/S sensor and a GPSAR. This paper will discuss the comparative experimental study using the recent co-located field scanning results.