Kluwer, Advances in Natural and Technological Hazards Research, p. 225-236, 2013
DOI: 10.1007/978-3-319-00972-8_20
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This study investigates slope stability for a relatively small scale (5.7 km(2), 0.6 km(3)), 8 kyr old landslide named Northern Twin Slide (NTS) at the slope of the Gela Basin in the Sicily Channel (central Mediterranean). The NTS is characterized by two prominent failure scars, forming two morphological steps of 110 and 70 m height. Geotechnical data from a drill core upslope the failure scar (GeoB14403) recovered sediments down to similar to 52 m below seafloor (mbsf). The deposits show low over consolidation ratio (OCR = 0.24-0.4) and low internal friction angle (20-22 degrees) around 28-45 mbsf, which suggests this mechanically weak interval may act as potential location of instability in a future failure event. Oedometer tests attest the sediments are highly under consolidated and the average overpressure ratio (lambda*) is similar to 0.7. Slope stability analyses carried out for different scenarios indicate that the slope is stable both under static undrained and drained conditions. A relatively small horizontal acceleration of 0.03-0.08 g induced by an earthquake may be sufficient to cause failure. We propose that moderate seismic triggers may have been responsible for the twin slide formation and could also cause mass wasting in the future.