Mass movement in Cordón de las Osamentas, de La Flecha river basin, San Juan, Argentina

Abstract

The de La Flecha river basin is located to the southwest of San Juan Province at around 31°50′ S, 68°57′ W. In this area a total of twenty debris-rock slides, in the Cordón de las Osamentas, were mapped and studied. The mode of failure of each was determined to be a rotational slide. The areal extent of the smallest observable landslide body is approximately 0.58 km2 and the largest is 367.76 km2. The slides were detected through high resolution satellite imagery interpretation, digital elevation models and field surveys, by identifying both the landslide detachment zones and landslide bodies based on the Geographic Information System (GIS). The slides have varying controlling factors, including lithology and slope, which seem to be the main controlling factors in causing slope instability. The spatial relationships among the landslides and the distribution of seismic epicentres, historical earthquakes and Quaternary faults (Maradona, Las Osamentas, Papagayos faults, La Chilca and El Mocho faults) were analysed. These gravitational movements were triggered by seismic shocks associated with active faults.