The application of ground-penetrating radar to investigate the subsurface structure of polygonal patterned ground

Abstract

Patterned ground is a group term for the more or less symmetrical forms, such as circles, polygons, nets, steps and stripes. It is a characteristic geomorphic feature formed by cyclic freezing and thawing of decimeter- to meter-thick soil layers in polar and high alpine environments. Despite the problems of process identification and accurate dating, patterned ground still has potential value as a climatic indicator in Quaternary sediments. Patterned ground is well developed over large areas in the ice-free regions of the King George Island, South Shetland Islands, West Antarctica. It has a sorted appearance commonly due to a border of stones surrounding finer materials. Although patterned ground has been extensively studied, the processes involved in patterned ground formation is not fully understood. In order to clarify the mechanism of pattern formation, it is necessary to investigate the subsurface structure of patterned ground. In this study, therefore, ground-penetrating radar (GPR) surveys on polygonal patterned ground were carried out to evaluate the usefulness of GPR method for this application. GPR surveys were performed at two sites using two frequencies (250 and 500 MHz), and detailed three-dimensional images of the subsurface beneath polygonal patterned ground were obtained successfully. It also provide valuable information on the depth of permafrost in the Barton Peninsula. Overall, GPR turned out to be a powerful tool to investigate the subsurface structure, without the need to disturb the polygonal patterned ground. However, further study is needed to improve the resolution of GPR survey on the patterned ground.