Ingeniería (Dr.)

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12404/9314

Browse

Filter results by typing the first few letters
Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Grandes deslizamientos en el flanco occidental de los Andes Centrales: inventario, caracterización y factores temporales
    (Pontificia Universidad Católica del Perú) Delgado Madera, Gabino Fabrizio; Benavente Escobar, Carlos Lenin; Schwartz, Stéphane; Zerathe, Swann
    Landslides are responsible for economic losses and deaths around the world. Large landslides also play an active role in the erosion and geomorphological evolution of mountains. They can be triggered by multiple factors including climatic and tectonic forcing’s. However, the respective roles climate variations and long-term tectonic on landslide processes remain poorly known because of a lack of chronological data on landslide occurrences over suitable time-scales. The western flank of the Central Andes presents interesting possibilities to study those questions because it offers landscapes and old sequences of mass movements that have been well preserved since hundreds of thousand years due to a dominant arid climate. In this context the aim of this thesis was to conduct a pluri-disciplinary work to better understand the factors controlling and triggering the large landslides in the Central arid Andes. For this purpose, we combined field geomorphology, SIG analysis and absolute dating at different spatial scales (i) a regional-scale landslide inventory; (ii) a local focus on an emblematic giant landslide for dating and geomorphological reconstructions, and (iii) a more systematic dating of landslides at the scale of a valley. Firstly, in order to identify the factors controlling landslide formation at a regional scale along the Central Andes, we inventoried all the large landslides (areas >0.1 km²) between the latitude 15 and 20°S. A thousand landslides were mapped, identifying two dominant typologies: rockslides (86%) and rock avalanches (14%). By statistical exploring this landslide database, it was identified a dominant lithological and relief control. The spatial distribution of the landslides reveals the presence of landslide clusters close to the crustal faults. Secondly, we conducted a focused study on the giant Aricota landslide, located in the southern Peru, in order to know when and in which conditions this large mass movement occurred. Detailed geomorphological mapping and cosmogenic nuclide dating (10Be) were applied revealing the occurrence of two failure events: (i) first a rockslide of ~2 km3 dated at 17.9 ± 0.7 ka, which dam the the valley and formed the Aricota lake (~6 km long), (ii) second a smaller rock-avalanche dated at 12.1 ± 0.2 ka, which was deposited on top of the first event. This chronology correlates well with two major paleo wet periods recorded on the Altiplano during the Younger Dryas and the Henrich 1st stadial, suggesting that the transition from arid to more humid climate may have influenced the formation of this landslide. Thirdly, in order to document more patterns of landslide occurrence though time and to further investigate their triggering, we replicated the dating procedure on eight other large landslides located all around the Aricota rockslide (the Locumba landslide cluster). The results indicated that they all occurred during the Pleistocene. Precise ages were obtained for four cases: the Cotana rockavalanche at ca. 16 ka, the Antavilca rock-avalanche at ca. 18 ka, the Quilahuani rock-avalanche at ca. 114 ka and the Angostura rockslide at ca. 205 ka. However, strong ages dispersion attributed to problems due cosmogenic nuclide inheritance have affected the others hampering robust dating. Those additional chronological constraints did not favor the hypothesis that the Locumba landslide cluster formed during a single event such as a single mega earthquake. Alternatively, the almost systematic correlation of landslide timing with paleo wet periods, including the "Ouki humid event" (ca. 100-120 ka) during the MIS5, rather support a dominant climate forcing although the co-effect of local seismicity cannot be ruled out.