1,720,964 research outputs found
Volcanic unrest at Nevados de Chillán (Southern Andean Volcanic Zone) from January 2019 to November 2020, imaged by DInSAR
Get PDFThe volcanic complex of Nevados de Chillan, ´ located in the Southern Volcanic Zone (SVZ) of the Andes, has been active for the past 640 ± 20 ka. Its volcanic activity includes dome forming eruptions, explosive events, and lava flows. The most recent eruption cycle started in January 2016. We employ DInSAR time-series from Sentinel-1 data to investigate the unrest episode from January 2019 to November 2020. Two distinct periods of unrest are recognized in the time series. The first period (from January to October 2019) coincides with explosive events, dome growth inside the active crater, and a decrease in seismic activity but does not present a significant deformation. The second period (October 2019 to November 2020) is characterized by a displacement towards the sensor’s line-of-sight of 100–120 mm. The observed surface deformation is compatible with an inflation source approximately 1.5 km south-southwest of the present active vent, at 5.5 ± 0.5 km depth from the surface, and with a volume change of 0.044 ± 0.014 km3 . The most likely explanation for the observed inflation of Nevados de Chillan is the intrusion of magma in a reservoir feeding the current eruption cycle.Fil: Astort, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Boixart, Gregorio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Folguera, Andrés. Universidad de Buenos Aires; ArgentinaFil: Battaglia, Maurizio. Università di Roma; Italia. U.S. Geological Survey, Volcano Disaster Assistance Program; Estados Unido
Geodynamic study of the volcanic centers of Auca Mahuída and Domuyo using geophysical data
No full textA lo largo de este trabajo se presentarán evidencias de distintos procesos dinámicos actuales en dos centros volcánicos, el Auca Mahuída y Domuyo, considerados latentes y/o extintos por no presentar registros históricos de erupciones. Si bien cada centro tiene su propia historia con características únicas, ambos centros volcánicos se localizan sobre una extensa y anómala área de magmatismo en el retroarco de la Cordillera de los Andes, distanciados entre sí por 200 km y con edades menores a los 2 Ma. A través de diferentes metodologías geofísicas, geodésicas y morfométricas, se analizarán las actividades anómalas detectadas en estos sitios. El centro volcánico Auca Mahuída corresponde al volcán más austral de La Payenia, donde abundantes evidencias geofísicas y geoquímicas advierten acerca de una configuración tectónica compleja que involucra un desgarro de la losa subducida y un flujo astenosférico ascendente interpretado como una pluma en trabajos previos. Los efectos causados por el impacto de este flujo astenosférico en la región han sido foco de estudio en la primera parte de esta Tesis. Se ha caracterizado la corteza y el manto estratosférico identificando una anomalía de la ondulación del geoide que puede asociarse con la huella del flujo astenosférico. A partir de datos gravimétricos y magnetométricos, se han computado mapas regionales del espesor elástico, de las profundidades del Moho y de la isoterma de Curie. Los resultados son consistentes con el escenario descripto por diversos autores como una anomalía astenosférica impactando y alimentando el volcanismo del área y desviando hacia arriba tanto su estructura térmica como la estructura de densidades. A partir del magnetismo de la zona se ha detectado la presencia de una extensa anomalía circular ubicada al este del volcán Auca Mahuída, cuya fuente se ubica a los ∼17 km de profundidad y se superpone con altos gravimétricos. Además, esta anomalía magnética presenta una alta correlación espacial en superficie con la pluma interpretada en profundidad, permitiendo inferir que se trata de un cuerpo máfico y denso posiblemente asociado al mismo flujo astenosférico. Diversas ramificaciones de esta anomalía magnética son observadas en los niveles superiores conectándose con el campo basáltico del volcán Auca Mahuída. Inestabilidades en los cauces de los ríos principales que drenan el área junto con un domamiento topográfico resultan coincidentes con los máximos de esta anomalía magnética, posiblemente como consecuencia del emplazamiento de grandes cuerpos máficos en la corteza. La segunda parte de la Tesis se centra en el Complejo Volcánico Domuyo, ubicado entre el borde occidental de La Payenia y el arco volcánico con productos magmáticos ácidos que lo diferencia del magmatismo típico de La Payenia y del arco volcánico. Una intensa deformación del terreno fue detectada mediante la metodología DInSAR, a partir de la cual se pudo estimar una velocidad anual de deformación aproximada de 12.5 cm·años−1 para el período comprendido entre 2014-2018. A partir de los patrones de deformación detectados, un modelado inverso es realizado para estimar la geometría y profundidad de la fuente. Por otro lado, los datos gravimétricos terrestres revelan un mínimo gravimétrico coincidente con el patrón de deformación superficial. Esta anomalía gravimétrica es interpretada como la señal de la misma fuente de deformación. Un modelo tridimensional de densidades fue ajustado a la anomalía gravimétrica, restringiendo la profundidad y geometría del cuerpo fuente con los resultados obtenidos previamente. De esta forma, a partir de estos resultados se propone la existencia de un reservorio ubicado entre los 4-7 km de profundidad, con un volumen aproximado de 160-187 km3 y una geometría prismática alargada orientada NS. Finalmente, un cúmulo de sismos es observado en el borde oeste de la deformación, coincidente espacialmente con la actividad hidrotermal, neotectónica e inestabilidades en los cauces de ríos y arroyos del área.This work characterizes using geophysical, geodetic and morphometric methodologies dynamic processes taking place in two volcanic centers, Auca Mahuída and Domuyo, considered dormant and/or even extinct, with no historical records of eruptions. Although each volcanic center has its own history with unique characteristics, both centers are located over a broad and anomalous magmatism area on the backarc of the Southern Central Andes, with ages younger than 2 Ma and separeted by 200 km from each other. The Auca Mahuída volcanic center is located in the southernmost area of the volcanis province La Payenia, where strong geophysical and geochemical tools evidence a complex tectonic configuration that involves a tearing of the subducted Nazca slab and an upwelling astenospheric flux that has been interpreted as a plume in previous works. The effects caused by the impact of this asthenospheric flux in the region have been the focus of study in the first part of this thesis. The crust and lithospheric mantle have been characterized by identifying an anomaly of the geoid undulations, that can be associated with the upward footprint of the asthenospheric flux. From gravimetric and magnetometric data, regional maps of the elastic thickness, depth of the crust-mantle discontinuity and the Curie isotherm have been computed. The results are consistent with the scenario described by various authors as an asthenospheric anomaly impacting and fueling the volcanism of the area and deflecting its thermal and density structure. The magnetism of the area shows the presence of an extensive semicircular anomaly located eastward of the Auca Mahuída volcano, whose source is located at ∼17 km depth and overlaps with a gravimetric high. In addition, this magnetic anomaly presents a high spatial surface correlation with the plume interpreted in-depth. This correlation allows inferring that a mafic and dense body is present, possibly associated with the same asthenospheric flux. Several ramifications of this magnetic anomaly are observed in the upper levels connecting with the basaltic field of the Auca Mahuída volcano. Instabilities in the channels of the main rivers that drain the area along with a topographic swell are coincident with the maximum of this magnetic anomaly, possibly as a result of the emplacement of large mafic bodies in the crust. The second part of the thesis focuses on the Domuyo Volcanic Complex, located on the western edge of La Payenia, 60 km from the volcanic arc. An intense deformation of the terrain was detected from DInSAR methodology, from which it is possible to estimate an annual velocity of deformation of approximately 12.5 cm·yr−1, for the period between 2014-2018. From the deformation patterns detected, inverse modeling was performed to estimate the geometry and depth of this source. On the other hand, terrestrial gravimetric data reveals a negative contrast density anomaly coinciding with the surface deformation pattern. This gravimetric anomaly is interpreted as the signal of the same causal source of the deformation. A three-dimensional density model was adjusted to the gravimetric anomaly, restricting the depth and geometry of the body source with the results obtained previously. Based on the results obtained, the existence of a reservoir located between 4-7 km depth, with an approximate volume of 160-187 km3 and an elongated prismatic geometry NS oriented, is proposed. Finally, a cluster of earthquakes is observed at the western edge of the deformation zone, with a spatial coincidence with the hydrothermal and neotectonic activity of the area. In addition, from the morphometric analysis carried out in the drainage network of Cerro Domuyo, instabilities in river and stream channels are identified in this same area.Fil: Astort, Ana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Geodynamic study of the volcanic centers of Auca Mahuída and Domuyo using geophysical data
Get PDFA lo largo de este trabajo se presentarán evidencias de distintos procesos dinámicos actuales en dos centros volcánicos, el Auca Mahuída y Domuyo, considerados latentes y/o extintos por no presentar registros históricos de erupciones. Si bien cada centro tiene su propia historia con características únicas, ambos centros volcánicos se localizan sobre una extensa y anómala área de magmatismo en el retroarco de la Cordillera de los Andes, distanciados entre sí por 200 km y con edades menores a los 2 Ma. A través de diferentes metodologías geofísicas, geodésicas y morfométricas, se analizarán las actividades anómalas detectadas en estos sitios. El centro volcánico Auca Mahuída corresponde al volcán más austral de La Payenia, donde abundantes evidencias geofísicas y geoquímicas advierten acerca de una configuración tectónica compleja que involucra un desgarro de la losa subducida y un flujo astenosférico ascendente interpretado como una pluma en trabajos previos. Los efectos causados por el impacto de este flujo astenosférico en la región han sido foco de estudio en la primera parte de esta Tesis. Se ha caracterizado la corteza y el manto estratosférico identificando una anomalía de la ondulación del geoide que puede asociarse con la huella del flujo astenosférico. A partir de datos gravimétricos y magnetométricos, se han computado mapas regionales del espesor elástico, de las profundidades del Moho y de la isoterma de Curie. Los resultados son consistentes con el escenario descripto por diversos autores como una anomalía astenosférica impactando y alimentando el volcanismo del área y desviando hacia arriba tanto su estructura térmica como la estructura de densidades. A partir del magnetismo de la zona se ha detectado la presencia de una extensa anomalía circular ubicada al este del volcán Auca Mahuída, cuya fuente se ubica a los ∼17 km de profundidad y se superpone con altos gravimétricos. Además, esta anomalía magnética presenta una alta correlación espacial en superficie con la pluma interpretada en profundidad, permitiendo inferir que se trata de un cuerpo máfico y denso posiblemente asociado al mismo flujo astenosférico. Diversas ramificaciones de esta anomalía magnética son observadas en los niveles superiores conectándose con el campo basáltico del volcán Auca Mahuída. Inestabilidades en los cauces de los ríos principales que drenan el área junto con un domamiento topográfico resultan coincidentes con los máximos de esta anomalía magnética, posiblemente como consecuencia del emplazamiento de grandes cuerpos máficos en la corteza. La segunda parte de la Tesis se centra en el Complejo Volcánico Domuyo, ubicado entre el borde occidental de La Payenia y el arco volcánico con productos magmáticos ácidos que lo diferencia del magmatismo típico de La Payenia y del arco volcánico. Una intensa deformación del terreno fue detectada mediante la metodología DInSAR, a partir de la cual se pudo estimar una velocidad anual de deformación aproximada de 12.5 cm·años−1 para el período comprendido entre 2014-2018. A partir de los patrones de deformación detectados, un modelado inverso es realizado para estimar la geometría y profundidad de la fuente. Por otro lado, los datos gravimétricos terrestres revelan un mínimo gravimétrico coincidente con el patrón de deformación superficial. Esta anomalía gravimétrica es interpretada como la señal de la misma fuente de deformación. Un modelo tridimensional de densidades fue ajustado a la anomalía gravimétrica, restringiendo la profundidad y geometría del cuerpo fuente con los resultados obtenidos previamente. De esta forma, a partir de estos resultados se propone la existencia de un reservorio ubicado entre los 4-7 km de profundidad, con un volumen aproximado de 160-187 km3 y una geometría prismática alargada orientada NS. Finalmente, un cúmulo de sismos es observado en el borde oeste de la deformación, coincidente espacialmente con la actividad hidrotermal, neotectónica e inestabilidades en los cauces de ríos y arroyos del área.This work characterizes using geophysical, geodetic and morphometric methodologies dynamic processes taking place in two volcanic centers, Auca Mahuída and Domuyo, considered dormant and/or even extinct, with no historical records of eruptions. Although each volcanic center has its own history with unique characteristics, both centers are located over a broad and anomalous magmatism area on the backarc of the Southern Central Andes, with ages younger than 2 Ma and separeted by 200 km from each other. The Auca Mahuída volcanic center is located in the southernmost area of the volcanis province La Payenia, where strong geophysical and geochemical tools evidence a complex tectonic configuration that involves a tearing of the subducted Nazca slab and an upwelling astenospheric flux that has been interpreted as a plume in previous works. The effects caused by the impact of this asthenospheric flux in the region have been the focus of study in the first part of this thesis. The crust and lithospheric mantle have been characterized by identifying an anomaly of the geoid undulations, that can be associated with the upward footprint of the asthenospheric flux. From gravimetric and magnetometric data, regional maps of the elastic thickness, depth of the crust-mantle discontinuity and the Curie isotherm have been computed. The results are consistent with the scenario described by various authors as an asthenospheric anomaly impacting and fueling the volcanism of the area and deflecting its thermal and density structure. The magnetism of the area shows the presence of an extensive semicircular anomaly located eastward of the Auca Mahuída volcano, whose source is located at ∼17 km depth and overlaps with a gravimetric high. In addition, this magnetic anomaly presents a high spatial surface correlation with the plume interpreted in-depth. This correlation allows inferring that a mafic and dense body is present, possibly associated with the same asthenospheric flux. Several ramifications of this magnetic anomaly are observed in the upper levels connecting with the basaltic field of the Auca Mahuída volcano. Instabilities in the channels of the main rivers that drain the area along with a topographic swell are coincident with the maximum of this magnetic anomaly, possibly as a result of the emplacement of large mafic bodies in the crust. The second part of the thesis focuses on the Domuyo Volcanic Complex, located on the western edge of La Payenia, 60 km from the volcanic arc. An intense deformation of the terrain was detected from DInSAR methodology, from which it is possible to estimate an annual velocity of deformation of approximately 12.5 cm·yr−1, for the period between 2014-2018. From the deformation patterns detected, inverse modeling was performed to estimate the geometry and depth of this source. On the other hand, terrestrial gravimetric data reveals a negative contrast density anomaly coinciding with the surface deformation pattern. This gravimetric anomaly is interpreted as the signal of the same causal source of the deformation. A three-dimensional density model was adjusted to the gravimetric anomaly, restricting the depth and geometry of the body source with the results obtained previously. Based on the results obtained, the existence of a reservoir located between 4-7 km depth, with an approximate volume of 160-187 km3 and an elongated prismatic geometry NS oriented, is proposed. Finally, a cluster of earthquakes is observed at the western edge of the deformation zone, with a spatial coincidence with the hydrothermal and neotectonic activity of the area. In addition, from the morphometric analysis carried out in the drainage network of Cerro Domuyo, instabilities in river and stream channels are identified in this same area.Fil: Astort, Ana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
