f AVO RELATIONSHIPS OF BURIED LANDMINE SURROGATES IN VARIABLE HYDROLOGIC CONDITIONS

Ground-penetrating radar has been extensively employed for the identification of unexploded ordinances (UXOs) through the use of various signal processing algorithms. Many of these studies however, fail to account for variable hydrologic conditions in the subsurface, which can cause significant changes in electromagnetic wave behavior. In order to develop understanding of these effects, several controlled irrigation experiments were conducted in a sand tank (1.5m x 1.5m x 0.8m) containing a buried anti-personnel landmine surrogate to determine the electromagnetic response as a function of antenna offset and hydrologic state. An automated 900MHz radar system consisting of a stationary ground-coupled transmitter accompanied by an elevated mobile receiver collected WARR data sections at 21 offsets (0.4-0.9m) in 0.5 minute intervals while a flux of water was applied. This unique form of transient data collection produces a rich 3D GPR data cube with axes of experiment time (min), antenna offset (m), and travel time (ns), which allowed common and multi-offset projections to be generated which greatly assisted in data analysis, including reflection amplitude variations with offset (AVO). AVO relationships for the land mine surrogate indicate that significant information is available which will help quantify the effect of hydrologic state on the data and improve target identification success using GPR. Transient data also indicates that high water content conditions, such as after a rainfall event, may provide a better environment for UXO identification, as the groundwave arrival is suppressed, minimizing wave interference. No full