A COMPLEX LANDSLIDE NEAR VILLAVICENCIO, COLOMBIA, ITS LANDSLIDE HAZARD

In the Colombian Eastern Cordillera 7 km west of the city of Villavicencio, located in the Llanos Foothills was ocurred a complex landslide is carried out, which was located in the slope mountain that conform the hanging wall of Servita thrust fault, This landslide began developed in June 23, 2017 affecting a section of the Bogotá - Villavicencio highway, and a small village with ~ 200 inhabitants. Its was active for about a year, being its last activations in the second rainy season (Tropical rainforest climate), in October 2018. The affectation area by landslide was 627,305 m2, with 5 m undercut. The average slope was 45°. A complex landslide type was found according to the Varnes´s classification because three different types of movement were identified in it. Rock fall on top near the crown. Creep that had 3 m/year approximated speed affected the largest area. The third process was presented with the development of small creek that led to the generation of a debris flow that affected the road and homes. The identified material were debris made up of blocks, gravel, sand, soil with remnants of plant material such as logs, and mainly grass. The affected rock unit was identified as the Lower Carboniferous Lutitas de Pipiral Formation that consists of highly fractured and weathered mudstones, sandstones, and siltstones layers. Prior to the development of this landslide, June 12 2017 a Mw 4.3 earthquake and hypocenter deep 0,1 km, and was located by the Colombian Seismological Network in the area affected by the landslide. This may have been the early trigger for the landslide. Cattle is the activity that affects the soils in this area. In this Colombian region, which has high tectonic activity, in addition to this landslide, the landslides have always been found to occur in high rainfall seasons, they are of the complex type, with a large volume of material removed, with high slopes, with fractured and severely weathered rocks, and where its soils have been affected by agricultural and cattle activities.