A prototype system for time-lapse acquisition of 2D electrical resistivity tomography (ERT) and time domain reflectometry (TDR) measurements was installed in a test site affected by a landslide in Basilicata region (southern Italy). The aim of the system is to monitor in real-time the rainwater infiltration into the soil and obtain information about the variation of the water content in the first layers of the subsoil and the possible influence of this variation on landslide activity. A rain gauge placed in the test site gives information on the rainfall intensity and frequency and suggests the acquisition time interval. The installed system and the preliminary results are presented in this paper. 1. Introduction Landslides are complex geological phenomena depending on many factors. In order to study these factors, to understand the triggering mechanisms of the movement, and to monitor its dynamic evolution it is necessary to apply a multidisciplinary approach. The rainwater infiltration into the soil and the increase of pore water pressure in the vadose zone can be considered one of the main causes of shallow landslides triggering. Usually, the standard techniques used to measure the water content of the soil and the water table levels in areas of potential instability are the TDR method and the piezometric measurements, respectively. These techniques, while allowing to obtain direct information of the considered parameter, provide only 1D information. Considering that landslides are volumetric phenomena it is a clear need to experiment new investigation techniques which can provide at least 2D hydrological information. It would be better if this information could be continuous in time. Recently, the literature reports many examples of application of indirect (geophysical) methods for the study and the estimate of water content in the first layers of the subsoil. Among these, the electrical resistivity tomography (ERT), usually applied to obtain information about the geometrical features of the landslides and estimate the thickness of the slide material [1–8], has been tested to obtain information on the temporal and spatial patterns of water infiltration processes [9–15]. The aim of this work is to present a prototype system planned to obtain time-lapse 2D ERT and TDR measurements in a landslide area located in Basilicata region (southern Italy). The system was planned with the aim to estimate the variation of electrical resistivity and soil moisture values in a long period and to obtain information about the influence of precipitations and seasonal
References
[1]
C. De Baria, V. Lapennaa, A. Perronea, C. Puglisi, and F. Sdao, “Digital photogrammetric analysis and electrical resistivity tomography for investigating the Picerno landslide (Basilicata region, southern Italy),” Geomorphology, vol. 133, no. 1-2, pp. 34–46, 2011.
[2]
V. A. Bogoslovsky and A. A. Ogilvy, “Geophysical methods for the investigation of landslides,” Geophysics, vol. 42, no. 3, pp. 562–571, 1977.
[3]
J. P. T. Caris and T. W. J. Van Asch, “Geophysical, geotechnical and hydrological investigations of a small landslide in the French Alps,” Engineering Geology, vol. 31, no. 3-4, pp. 249–276, 1991.
[4]
F. Ferrucci, M. Amelio, M. Sorriso-Valvo, and C. Tansi, “Seismic prospecting of a slope affected by deep-seated gravitational slope deformation: the Lago Sackung, Calabria, Italy,” Engineering Geology, vol. 57, no. 1-2, pp. 53–64, 2000.
[5]
V. Lapenna, P. Lorenzo, A. Perrone, S. Piscitelli, E. Rizzo, and F. Sdao, “2D electrical resistivity imaging of some complex landslides in the Lucanian Apennine chain, southern Italy,” Geophysics, vol. 70, no. 3, pp. B11–B18, 2005.
[6]
D. Jongmans and S. Garambois, “Geophysical investigation of landslides: a review,” Bulletin de la Societe Geologique de France, vol. 178, no. 2, pp. 101–112, 2007.
[7]
M. Pfaffhuber, S. Bastani, and M. Cornée, “Multi-method high resolutiongeophysical & geotechnical quick clay mapping A.A,” Near Surface. In press.
[8]
K. Sudha, M. Israil, S. Mittal, and J. Rai, “Soil characterization using electrical resistivity tomography and geotechnical investigations,” Journal of Applied Geophysics, vol. 67, no. 1, pp. 74–79, 2009.
[9]
D. Michot, Y. Benderitter, A. Dorigny, B. Nicoullaud, D. King, and A. Tabbagh, “Spatial and temporal monitoring of soil water content with an irrigated corn crop cover using surface electrical resistivity tomography,” Water Resources Research, vol. 39, no. 5, pp. SBH141–SBH1420, 2003.
[10]
D. H. Jayawickreme, R. L. van Dam, and D. W. Hyndman, “Subsurface imaging of vegetation, climate, and root-zone moisture interactions,” Geophysical Research Letters, vol. 35, no. 18, Article ID L18404, 5 pages, 2008.
[11]
R. De Franco, G. Biella, L. Tosi et al., “Monitoring the saltwater intrusion by time lapse electrical resistivity tomography: the Chioggia test site (Venice Lagoon, Italy),” Journal of Applied Geophysics, vol. 69, no. 3-4, pp. 117–130, 2009.
[12]
P. Brunet, R. Clément, and C. Bouvier, “Monitoring soil water content and deficit using electrical resistivity tomography (ERT)—a case study in the Cevennes area, France,” Journal of Hydrology, vol. 380, no. 1-2, pp. 146–153, 2010.
[13]
T. Arora and S. Ahmed, “Characterization of recharge through complex vadose zone of a granitic aquifer by time-lapse electrical resistivity tomography,” Journal of Applied Geophysics, vol. 73, no. 1, pp. 35–44, 2011.
[14]
J. Travelletti, P. Sailhac, J.-P. Malet, G. Grandjean, and J. Ponton, “Hydrological response of weathered clay-shale slopes: water infiltration monitoring with time-lapse electrical resistivity tomography,” Hydrological Processes. In press.
[15]
G. Cassiani, V. Bruno, A. Villa, N. Fusi, and A. M. Binley, “A saline trace test monitored via time-lapse surface electrical resistivity tomography,” Journal of Applied Geophysics, vol. 59, no. 3, pp. 244–259, 2006.
[16]
T. Pescatore, P. Renda, and M. Tramutoli, “Rapporti tra le unità lagonegresi e le unità Sicilidi nella media valle del Basento (Appennino lucano),” Memoriali Società Geologica Italiana, vol. 41, pp. 353–361, 1988.
[17]
S. Gallicchio, M. Marcucci, P. Pieri, I. Premoli Silva, L. Sabato, and G. Salvini, “Stratigraphical data from a Cretaceus claystones sequence of the “Argille Varicolori” in the Southern Apennines (Basilicata, Italy),” Palaleopelagos, vol. 6, pp. 261–272, 1996.
[18]
R. Selli, “Il Paleogene nel quadro della geologia dell’Italia meridionale,” Memorie della Società Geologica Italiana, vol. 3, pp. 737–790, 1962.
[19]
M. H. Loke and R. D. Barker, “Rapid least-squares inversion of apparent resistivity pseudosections by a quasi-Newton method,” Geophysical Prospecting, vol. 44, no. 1, pp. 131–152, 1996.
