XIII Congreso Peruano de Geologa. Resmenes Extendidos Sociedad Geolgica del Per

58

GEOMORPHOLOGIC INVESTIGATION AND LANDSLIDE MONITORING AT MACHU PICCHU, PERU

Vt Vilmek1, Jan Klime2, Ji Zvelebil3, Fernando Astete4 & Julio Crdova4

1Dep. of geography and geoecology, Faculty of Scinece, Charles University, Prague, Czech Republic 2Institut of Rock Structures and Mechanics, Czech Academy of Sciences, Prague, Czech Republic

3Czech Geologic Survay, Prague, Czech Republic 4Instituto Nacional de la Cultura, Cusco, Peru

Landscape evolution of the area around the Inca's Town of Machu Picchu is dominated by slope movements, tectonic disturbance of the granite rocks and fluvial erosion. Landslides of different types, frequency and magnitude were mapped and described using aerial pictures, satellite images and field investigation through which the multi-temporal landslide inventory map has been prepared. The landslide inventory was integrated with the geomorphologic map of the Machu Picchu meander as well as with detailed mapping of the archeological site itself to identify potentially dangerous geomorphologic processes. The recent activity of large-scale landslides within the historic town is being monitored by network of dilatometric and extensometric profiles. The measurement sites were chosen so the activity of potential deep-seated landslides, dangerous for the historical buildings will be recorded. The results show movement up to 1 mm/year (3 years of measurements) on open cracks inside the archaeological site and up to 6 mm/2 years across the suggested scarp of the large-scale landslide (main Plaza). Therefore it seems that, occurrence of a large-scale catastrophically rapid slope collapse is improbable within the short time interval of months or several years, if present-day conditions will be maintained (e.g. absence of a strong earthquake). Spatial distribution of rock slides, rock falls and debris flows is strongly influenced by alignment between topography and joints. Archive data show that debris flows occur mostly between January and March with average return period of 2 years. Experiences of the April 10th 2004 Alcamayo River debris flow prove that expert based hazard maps may be the basis for successful mitigation strategy if are included in urban planning.