Susceptibilidad a la licuación de suelos y sedimentos en el valle Ullum-Zonda (31º30’ S-68º25’ O), Precordillera, Andes Centrales, Argentina

Abstract

. The earthquakes of 1894, 1944, 1952 and 1977 occurred in the province of San Juan in central-wesern Argentina caused numerous processes of soils and sediment liquefaction, including those in the Ullum-Zonda valley. Historical records showed cracks, sand volcanoes, craters and differential settlements, which caused significant damage to housing and the agro-industrial sector of the region. In this work, we carried out a study of the susceptibility to liquefaction of soils and sedimentary deposits in the Ullum-Zonda valley. This was conducted using a methodology in which conditioning factors such as depth of the water table, historical records of liquefaction, potential seismogenic sources, origin, age and grain size of the soils and sedimentary deposits, among others, were evaluated and weighted. An iterative process of overlapping maps weighted the influence of the different factors in the assessment of susceptibility. Once the optimal combination was achieved, a final map with the zoning of soils and sediment susceptibility to liquefaction was obtained for the Ulum-Zonda Valley. The achieved zoning was related to a susceptibility index (SI), qualitatively classified as very high, high, moderate and low. The zone of very high susceptibility to liquefaction is located in the distal portion of the alluvial fan formed by the San Juan River in the Ullum-Zonda Valley, the areas of high to moderate susceptibility in the middle sector of the fan, and those of moderate to low susceptibility correspond to the proximal-middle sector of the fan. The main villages of the Ullum-Zonda valley, Ibáñez (head of the Ullum department) to the north of the San Juan River, Basilio Nievas (head of the Zonda department), to the south of the river, Tacú residential sector (located south of the Ullum dam) and the yacht clubs (located on the northeast periphery of the dam) are located in the areas of high to very high susceptibility, where the main conditioning factors are soil and sediments granulometry and the depth of the phreatic level.

Irrigación de largo plazo como desencadenante de flujos de tierra en Chenque Malal, Norpatagonia argentina

“…Sin embargo, cabe señalar que la persistencia de la sequía durante 2020 se podría considerar como un agravante para el evento puesto que las condiciones cohesivas y freáticas preexistentes del suelo fueron modificadas ante el incremento anómalo y súbito de agua proveniente del canal de riego, lo que provocó un aumento de la presión de poro y una disminución de la resistencia de la ladera que condujeron a su colapso. En segundo lugar, los sismos han demostrado una influencia remarcable en la generación de deslizamientos en diferentes regiones del país (e.g., González Díaz et al, 2006;Carignano et al, 2014;Colavitto et al, 2021;Palacios et al, 2021;Ginesta Torcivia et al, 2022). En Chenque Malal, de acuerdo con las bases de datos sísmicos nacionales e internacionales consultadas (i.e., INPRES, IRIS y USGS), se registraron entre los años 1914 y 2020 cerca de seis mil sismos en un radio de 300 km, previo al colapso, lo que incluye el evento M w 9,5 ocurrido en 1960 en Valdivia, Chile.…”