Constraining melt geometries beneath the Afar Depression, Ethiopia from teleseismic receiver functions: the anisotropic H-κ stacking technique

Understanding the nature of the crust has long been a goal for seismologists when imaging the Earth. This is particularly true in volcanic regions where imaging melt storage and migration can have important implications for the size and nature of an eruption. Receiver functions and the H-κ stacking (Hκ) technique are often used to constrain crustal thickness (H) and the ratio of P to S wave velocities (κ). In this paper, I show that it is essential to consider anisotropy when performing Hκ. I show that in a medium with horizontally transverse isotropy a strong variation in κ with back azimuth is present, which characterizes the anisotropic medium. In a vertically transverse isotropic medium, no variation in κ with back azimuth is observed, but κ is increased across all back azimuths. Thus, estimates of κ are more difficult to relate to composition than previously thought. I extend these models to melt-induced anisotropy and show that similar patterns are observed, but with more significant variations and increases in κ. Based on these observations, I develop a new anisotropic H-κ stacking technique which inverts Hκ data for melt fraction, aspect ratio, and orientation of melt inclusions. I apply this to data for the Afar Depression and show that melt is stored in interconnected stacked sills in the lower crust, which likely supply the recent volcanic eruptions and dike intrusions. This new technique can be applied to any anisotropic medium where it can provide constraints on the average crustal anisotropy

El bachillerato con orientación en educación física en la Provincia de Córdoba. Una propuesta con potencial inclusivo y emancipador

A partir de lo establecido en la Ley de Educación Nacional Nº 26.206 y de las Resoluciones del Consejo Federal de Educación en relación con la obligatoriedad de la Educación Secundaria es posible establecer lineamientos para la construcción de propuestas formativas orientadas a garantizar el ingreso, permanencia y egreso de estudiantes en el tramo final de este nivel del sistema educativo. Éste es el marco en el cual se definen –en el orden nacional- 10 (diez) Orientaciones posibles para el último ciclo de la Educación Secundaria, entre las que se destaca el Bachillerato en Educación Física. El Ministerio de Educación de la Provincia de Córdoba, inicia el proceso de construcción participativa de los Diseños Curriculares Jurisdiccionales correspondientes e implementa diversos dispositivos de consulta

Seismic imaging of the lithospheric structure of the Zagros mountain belt (Iran)

International audienceWe present a synthesis and a comparison of the results of two temporary passive seismic experiments installed for a few months across Central and Northern Zagros. The receiver function analysis of teleseismic earthquake records gives a high-resolution image of the Moho beneath the seismic transects. On both cross-sections, the crust has an average thickness of 43±2 km beneath the Zagros fold-and-thrust belt and the Central domain. The crust is thicker beneath the hanging wall of the Main Zagros Reverse Fault (MZRF), with a larger maximum Moho depth in Central (69±2 km) than in Northern Zagros (56±2 km). The thickening affects a narrower region (170 km) beneath the Sanandaj-Sirjan zone of Central Zagros and a wider region (320 km) in Northern Zagros. We propose that this thickening is related to overthrusting of the crust of the Arabian margin by the crust of Central Iran along the MZRF considered as a major thrust fault cross-cutting the whole crust. The fault is imaged as a lowvelocity layer in the receiver function data of the Northern Zagros profile. Moreover, the crustal-scale thrust model reconciles the imaged seismic Moho with the Bouguer anomaly data measured on the Central Zagros transect. At upper mantle depth, P-wave tomography confirms the previously observed strong contrast between the faster velocities of the Arabian margin and the lower velocities of the Iranian micro-blocks. Our higher-resolution tomography combined with surface-wave analysis locates the suture in the shallow mantle of the Sanandaj-Sirjan zone beneath Central Zagros. The Arabian upper-mantle has shield-like shear-wave velocities, while the lower velocities of the Iranian upper mantle are likely due to higher temperature. But these velocities are not low enough and the low-velocity layer not thick enough to conclude on a delamination of the lithospheric mantle lid beneath Iran. The lack of a high-velocity anomaly in the mantle beneath Central Iran suggests that the Neotethyan oceanic lithosphere is probably detached from the Arabian margin

Caracterización de sequías hidrológicas en cuencas del centro y norte de la república Argentina

Práctica Supervisada (IC)--FCEFN-UNC, 2014Caracteriza las sequías desde un enfoque hidrológico, utilizando datos de los aportes anuales de 13 cuencas localizadas en el centro y norte de la República Argentina

Seismological evidence for crustal-scale thrusting in the Zagros mountain belt (Iran)

International audienceCrustal receiver functions computed from the records of 45 temporary seismological stations installed on a 620-km long profile across central Zagros provide the first direct evidence for crustal thickening in this mountain belt. Due to a rather short 14-km average station spacing, the migrated section computed from radial receiver functions displays the Moho depth variations across the belt with good spatial resolution. From the coast of the Persian Gulf to 25 km southwest of the Main Zagros Thrust (MZT), the Moho is almost horizontal with slight depth variations around 45 km. Crustal thickness then increases abruptly to a maximum of ~70 km beneath the Sanandaj-Sirjan metamorphic zone, between 50 and 90 km northeast of the surface exposure of the MZT. Further northeast, the Moho depth decreases to ~42 km beneath the Urumieh-Dokhtar magmatic assemblage and the southern part of the Central Iranian micro-continent. The region of thickest crust is located ~75 km to the northeast of the Bouguer anomaly low at –220 mgals. Gravity modelling shows that the measured Moho depth variations can be reconciled with gravity observations by assuming that the crust of Zagros underthrusts the crust of central Iran along the MZT considered as a crustal-scale structure. This hypothesis is compatible with shortening estimates by balanced cross-sections of the Zagros folded belt, as well as with structural and petrological studies of the metamorphic Sanandaj-Sirjan zone

Volcanic CO2 output at the Central American subduction zone inferred from melt inclusions in olivine crystals from mafic tephras

The volatile contents of olivine‐hosted (Fo89–71) melt inclusion glasses in rapidly quenched mafic tephras from volcanic front volcanoes of the Central American Volcanic Arc (CAVA) in Guatemala, Nicaragua, and Costa Rica, were analyzed by secondary ion mass spectrometry (SIMS) in order to derive the minimum eruptive output of CO2, along with H2O, Cl, and S. Details of the analytical method are provided that establish melt inclusion CO2 analyses with the Cameca ims6f at the Helmholtz Centre Potsdam. The highest CO2 concentrations (up to 1800 mg/g) are observed in Nicaraguan samples, while melt inclusions from Guatemala and Costa Rica have CO2 contents between 50 and 500 mg/g. CO2 does not positively covary with sediment/slab fluid tracers such as Ba/La, Ba/Th, or U/La. Instead, the highest CO2 concentrations occur in the inclusions with the most depleted incompatible element compositions and low H2O, approaching the composition of mid‐ocean ridge basalts (MORBs), whereas the most H2O‐rich inclusions are relatively CO2‐poor (<800 mg/g). This suggests that CO2 degassing was more extensive in the melts with the highest slab contribution. CO2/Nb ratios in the least degassed CAVA melt inclusions are similar to those of primitive MORBs. These are interpreted here as recording a minimum CO2 output rate from the mantle wedge, which amounts to 2.8 × 104 g/s for the ∼1100 km long CAVA. Previously published estimates from quiescent degassing and numerical modeling, which also encompassed the slab contribution, are 3 times higher. This comparison allows us to estimate the proportion of the total CO2 output derived from the mantle wedge

Caracterización del trasporte de sedimentos en un tramo del río Tercero (Ctalamochita) utilizando tecnología acústica doppler

Tesis (MCI Mención Recursos Hídricos)--FCEFN-UNC, 2017Caracteriza el transporte de sedimentos en un tramo del Río Tercero (Ctalamochita) utilizando tecnología acústica Doppler, desarrollando, validando e implementando una metodología rápida y segura para la cuantificación del transporte de sedimentos (Tanto en suspensión como de fondo) en condiciones de flujo de aguas medias y alta

Hydrous upwelling across the mantle transition zone beneath the Afar Triple Junction

The mechanisms that drive the upwelling of chemical heterogeneity from the lower to upper mantle (e.g., thermal versus compositional buoyancy) are key to our understanding of whole mantle con- vective processes. We address these issues through a receiver function study on new seismic data from recent deployments located on the Afar Triple Junction, a location associated with deep mantle upwelling. The detailed images of upper mantle and mantle transition zone structure illuminate features that give insights into the nature of upwelling from the deep Earth. A seismic low-velocity layer directly above the mantle transition zone, interpreted as a stable melt layer, along with a prominent 520 km discontinuity sug- gest the presence of a hydrous upwelling. A relatively uniform transition zone thickness across the region suggests a weak thermal anomaly (<100 K) may be present and that upwelling must be at least partly driven by compositional buoyancy. The results suggest that the lower mantle is a source of volatile rich, chemically distinct upwellings that influence the structure of the upper mantle, and potentially the chemis- try of surface lavas

Desarrollo de caramelos a base de jengibre y arándano

El Jengibre presenta propiedad carminativa, antiulcerosa, antiespasmódica, colagoga, protector hepático, antitusiva, expectorante y laxante. Se lo considera estimulante, rubefaciente y diaforético. Es utilizado cuando hay mala circulación y calambres. También se emplea en casos febriles como diurético. El Arándano se utiliza en problemas renales por su acción depurativa y desintoxicante, además se ha comprobado que posee propiedades antibacterianas que lo hacen muy adecuado para la prevención de cistitis. También se conocen sus propiedades antioxidantes, astringentes, antivomitivas, antiespasmódicas, antiinflamatorias, vasodilatadoras, antihemorrágicas, entre otras. El objetivo del presente trabajo es aprovechar las propiedades terapéuticas Jengibre (Zingiber officinale) y Arándano (Vaccinium macrocarpon). Para ello se desarrolló un procedimiento para obtener un caramelo en forma de pastilla comprimida, que aproveche las cualidades de los mismos, siendo utilizado como suplemento dietario y coadyuvante del tratamiento de ciertas patologías. El mismo se basa en un método de compresión por vía húmeda.Fil: Bergesio, Carla Dulcinea. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; ArgentinaFil: Ligorria, Triana Ayelén. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; Argentin

Nudos de discusión sobre la Formación Docente Universitaria en países del MERCOSUR

Una de las consecuencias de entender que los estudios superiores son un bien público y social, un derecho humano universal y una responsabilidad de los estados, tal como lo sostiene la Conferencia Regional de Educación Superior reunida en Cartagena de Indias (2008), es apostar fuertemente a la revisión de las prácticas docentes universitarias. En este artículo se presentan los resultados del proyecto “Construcción cooperativa de políticas y estrategias de formación de docentes universitarios en la región”, coordinado desde la Secretaría de Asuntos Académicos de la Universidad Nacional de Córdoba y con la participación de nueve universidades del Mercosur Educativo. El propósito central del proyecto fue “desarrollar redes de cooperación para el fortalecimiento de la formación docente universitaria (FDU) a nivel regional”. El grupo de universidades participantes se propusieron producir conocimientos sobre el estado de las políticas de formación docente en cada universidad y su relación con los sistemas de acceso, permanencia y promoción de los profesores. En este artículo se presentan, de manera sintética, las características del proyecto, la metodología desarrollada, algunos nudos de discusión sobre la docencia universitaria que tuvieron lugar en los encuentros con el grupo de universidades y, finalmente, desafíos o líneas de trabajo conjunto.  Palabras claves: Formación docente – universidad – profesorado universitari