Browsing by Author "Sanhueza, J."

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    Shallow Anatomy of the San Ramon Fault (Chile) Constrained by Geophysical Methods : Implications for its Role in the Andean Deformation
    (2020) Yáñez Carrizo, Gonzalo Alejandro; Pérez Estay, N.; Araya Vargas, J.; Sanhueza, J.; Figueroa, R.; Maringue, J.; Rojas, T.
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    Soil electrical resistivity monitoring as a practical tool for evaluating irrigation systems efficiency at the orchard scale: a case study in a vineyard in Central Chile
    (2021) Vargas, J. Araya; Gil, P. M.; Meza, F. J.; Yanez, G.; Menanno, G.; Garcia-Gutierrez, V; Luque, A. J.; Poblete, F.; Figueroa, R.; Maringue, J.; Perez-Estay, N.; Sanhueza, J.
    In many orchards, irrigation scheduling is designed based on data from meteorological networks and considering homogeneous soil properties. Such assumptions may result in inefficient irrigation, which is difficult to constrain without expensive or invasive techniques. Here we have evaluated the ability of the electrical resistivity tomography (ERT) for detecting meter-scale irrigation uniformity and deep percolation during irrigation. The spatiotemporal variability of soil volumetric water content (VWC) in a vineyard located near Santiago (Chile) was inferred using ERT monitoring of two irrigation cycles. The electrical resistivity structure up to 4 m depth was estimated using two-dimensional inversion of ERT data. ERT results were verified by comparing resistivity models with VWC measured with soil moisture sensors, soil properties mapped in a 2 m-depth soil pit, and the spatiotemporal evolution of VWC obtained by solving numerically Richards equation. Largest temporal variations of resistivity were observed within the root depth (1 m) and are consistent with expected relative changes in VWC during irrigation. ERT images exhibit lateral changes in resistivity at these depths, likely indicating non-uniform infiltration of water controlled by observed soil texture variations. Resistivity changes were also observed below the root zone, suggesting that a fraction of the irrigation water percolates downward. These findings can be explained by an excess of irrigation water applied during the monitoring, which was planned considering regional evapotranspiration (ET) data that overestimated the actual ET measured at the vineyard. Altogether, our results suggest that ERT monitoring during irrigation is a cost-effective tool to constrain the performance of irrigation systems.
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    The Role of Temperature in the Along-Margin Distribution of Volcanism and Seismicity in Subduction Zones: Insights From 3-D Thermomechanical Modeling of the Central Andean Margin
    (2021) Araya Vargas, J.; Sanhueza, J.; Yanez, G.
    The distribution of volcanic and seismogenic zones is segmented along the trench-parallel direction in the Central Andes, and factors controlling their clustering are not fully understood. Here we present a 3-D thermomechanical model of the subduction zone at 18 degrees-26 degrees S to examine the role that temperature and mantle flow play in the distribution of active volcanoes and seismicity. We applied a steady state approach in which solid-state flow is driven by a kinematically prescribed slab with realistic geometry (including changes along the Bolivian Orocline) and using a 3-D model of the continental crust thickness. The obtained temperature distribution is consistent with proxies for isotherms derived from independent geophysical data, except below the Eastern Cordillera at 21 degrees-23 degrees S. The computed mantle flow pattern reveals the presence of along-margin dynamic pressure gradients. This 3-D preferential flow results in mantle temperatures of 1200-1400 degrees C at 80-100 km depth below the arc, with comparatively higher temperatures at similar to 22 degrees-25 degrees S. The obtained along-margin variations in temperature and in estimated melt velocity suggest that the subarc mantle south of 22 degrees S exhibits more favorable conditions for generation and upward migration of partial melts. This segment coincides with the higher concentration of active arc volcanoes and the presence of the Altiplano-Puna Volcanic Complex in the backarc. Intermediate-depth seismicity concentrates roughly below where the slab top is at 400-800 degrees C, suggesting that temperature exerts some control on the first-order distribution of intraslab seismicity. However, most intraslab seismicity occur at pressure-temperature conditions which are outside of the stability field expected for key dehydration reactions in slabs.