GPS monitoring and new data on slope movements in the Maratea Valley (Potenza, Basilicata)

Abstract

Large-scale earth movements in the Maratea valley involving the inhabited area (Basilicata, Italy) have already been the object of scientific studies. These dislocate the outcropping clayey formations and the superimposed masses made up of detritus, carbonate units and large blocks, especially on the left side of the valley. Initial data on earth movements were obtained by the variation in distances monitored by an infrared distance-meter instrument (EDM), between 1983 and 1996. The present study brings out the results obtained by three successive high precision GPS monitoring campaigns undertaken between 1997 and 2000, on a grid of approximately 50 bench-marks. This process was supplemented by EDM monitoring carried out on a wider network of bench-marks than previously imposed. A comparison of different maps and other historical measurements complete the picture. The presence of sustained movements in correspondence with the outcropping clays in the lower part of the valley was confirmed, while such movements are drastically reduced on the detritus and large dislocated carbonate units and blocks, which occupy almost uninterruptedly the left side and the upper parts of the valley. Overall, the arrangement of the vectors allows us to achieve a first model of the on-going gravitational processes in the valley which appear to be attributable to a composite landslide: a spreading evolving lower-down into a large and deep flow. These processes should affect the dislocation of Carbonate Units on the so-called Sackung of Maratea, whose instability and causes are still being studied.