9712012 Liu This grant provides partial support for acquisition of additional ground penetrating radar (GPR) antennas, a workstation and a PC for the shallow geophysics program at the University of Connecticut. Three GPR antennas at frequencies of 25, 200 and 1000 MHz will be purchased to examine the attenuation of GPR signals through various geological and structural environments. The computers will be used for data acquisition and subsequent inversions and modeling. Together with research support from a companion geophysics proposal, the PI will develop a non-linear frequency dependence model for high resolution GPR tomography of soils and the shallow crust and will investigate the propagation of radar signals through inhomogeneous strata. The potential of improved GPR tomographic techniques to problems of environmental significance (i.e. mapping contaminated groundwater plumes) warrants continued development of this geophysical technique. ***