http://hdl.handle.net/2122/149 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/3573 Title: On the shape of reflecting surfaces investigated by a 60 MHz radar <br/> <br/>Authors: Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tabacco, I. E.; Universita` di Milano — Sezione Geofisica, Milan, Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: Radio echo sounding (RES) systems for ice thickness measurements are practically the only suitable equipment for large-scale radar flight surveys in polar regions. The length of the radio wave carrier does not allow the employment of sophisticated antennas, so folded dipoles are used, arranged beneath the wings. As a consequence, the transmitted radio wave beam illuminates a relatively large area, making the power of the echo signal related in a significant way to the shape of the reflecting surfaces. An electromagnetic analysis shows that the amplitude variations detected by the system, under certain conditions, are mainly due to focusing or defocusing effects determined by the shape of the reflectors. Tue, 29 Oct 2002 22:58:59 GMT http://hdl.handle.net/2122/1448 Title: A geoelectrical survey above an Antarctic ice shelf <br/> <br/>Authors: Merlanti, F.; Dipartimento di Scienze della Terra, Universitá di Genova, Italy; Pavan, M.; Dipartimento di Scienze della Terra, Universitá di Genova, Italy <br/> <br/>Abstract: A geoelectrical survey was performed on the Hells Gate ice shelf (Victoria Land-Antarctic) within the framework of an integrated geophysical and glaciological research program. The resistivity profiles show a similar trend, with resistivity values ranging from about 25000 W · m to 500000 W · m. These results have been interpreted as the effect of a sharp transition from "marine ice" to "continental" ice an interpretation that is consistent with the results of surface mapping. Interpreting the Vertical Electrical Soundings (VES) is a complex process. In fact, the alternating layers of ice with different compositions and salt content generate great uncertainty relative to the corresponding electric stratigraphies. To solve these problems of equivalency, all the available constraints were used including the drilling thickness, seismic reflection profiles as well as radar profiles. The results were used to provide what is mainly a qualitative overview that is coherent with the glaciological hypotheses relative to the evolution and structure proposed by some researchers for this ice shelf. Wed, 29 Jul 1998 22:58:59 GMT