1,720,995 research outputs found
Multichannel seismic processing applied to FR16 line from Western Iberian margin
No full textTrabajo final presentado por María Alcaide García para el Máster en Reservoir Geology and Geophysics de la Universitat de Barcelona (UB) y la Universitat Autònoma de Barcelona (UAB), realizado bajo la dirección del Dr. Rafael Bartolomé y la Dra. Alcinoe Calahorrano del Institut de Ciències del Mar (ICM-CSIC) y de la Dra. Ana Sotomayor García.-- 25 pages, 26 figures, 1 tableThis research work aims to deepen the understanding of the seismic reflection method and the analysis and processing of multichannel seismic data. Here it is presented an overview of the seismic method and the main steps usually performed during the processing sequence and its theoretical basis. To achieve this, the processing modules will be used to produce a clean image of the FR16 profile, located on the Moroccan western coast and recorded during the FRAME cruise in a 2D multichannel seismic arrangement.
The first part of the thesis describes the theoretical bases of several processing steps, while the second part is dedicated to describing the processing workflow and tests performed for different steps, as well as the selected parameters to obtain the final image. A new result’s presentation by mobile figures is suggested, to facilitate the observation of the changes produced by the different processes and parameters in the data.
The followed workflow can be resumed in these four main points: normal move-out correction, deconvolution, de multiplexing, and migration. During the seismic data processing, the obtainment of a proper velocity model was one major challenge, because having an accurate stack velocity model is a key not only for the quality of the final image but also for several intermediate processes which are velocity depending (e.g. radon, F-K filters, DMO). It has been done a velocity picking and verifications after main processes like deconvolution, SRME, Radon, and DMO. Also, the difficulty of demultiplexing the traces has led to the employment of numerous demultiple jobs and filters, which are SRME, Radon and F-K filterings.
Noise, multiples, NMO effect and dipping events presented in the seismic raw data, have been mostly attenuated. The project result is a seismic line ready to be interpreted. Bibliographic research has served to interpret the line, and discussion of previous results has been mad
Appraisal of the Tectonic Structure of the Gulf of Cadiz and the Guadalquivir Basin from Seismic Images
No full textInciativa Ibérica para el Estudio de las Fallas Activas, Tercera Reunión Ibérica sobre Fallas Activas y Paleosismología IBERFAULT 2018 - Third Iberian Meeting on Active Faults and Paleoseismology, 11-13 June 2018, Alicante, Spain.-- 4 pages, 4 figures[EN] This work focus on verifying of the presence in depth of tectonic structures published in scientific articles in the area of the Gulf of Cadiz and the Guadalquivir Basin in order to obtain an update tectonic map of this zone. To do this, we first made a compilation of seismic and bathymetric data from public and private databases. Then, we made a compilation of scientific articles related with the tectonics of the region and selected the most representative tectonic maps. We geolocated these maps and digitized the different tectonic structures. Finally, these faults were verified in depth by using the seismic lines from our database. The first results do not validate numerous faults, especially on land, and indicate that the tectonic faults described and validated have not been active since ~ 7 Ma. Active tectonics in this area occurs on minor faults probably related to diapirism[ES] Este trabajo se encuadra en un proyecto que tiene por objetivo estudiar la estructura tectónica del Golfo de Cádiz y la Cuenca de Guadalquivir. En concreto, este primer análisis se centra en fallas de la región NE del Golfo de Cádiz y Cuenca de Guadalquivir de carácter regional con el fin de actualizar el mapa tectónico de esta zona. Para ello, se han recopilado estudios de la estructura y la actividad tectónica de la región y se han seleccionado mapas tectónicos con estructuras de decenas a centenares de kilómetros de continuidad lateral. Estos mapas han sido geolocalizados y las fallas digitalizadas para evaluarlas
utilizando datos sísmicos y batimétricos. Nuestro análisis indica que existen fallas publicadas que no muestran evidencias de deformación en las imágenes sísmicas del subsuelo y que son susceptibles de ser descartadas en un mapa actualizado. Asimismo, se ha verificado que diversas fallas publicadas aparecen como importantes estructuras del subsuelo pero que son inactivas desde hace ~7 Ma. Las estructuras activas observadas corresponden a fallas normales comparativamente menores, posiblemente relacionadas con diapirismoPeer Reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Naturaleza y formación de la Provincia Volcánica de Galápagos
No full text17 pages, 7 figures[ES] La Provincia Volcánica de Galápagos (PVG) es resultado de la interacción entre el punto caliente de Galápagos y la dorsal de Cocos-Nazca durante los últimos ~20 m.a. Esta interacción ininterrumpida ha producido un exceso de magmatismo de variable intensidad que ha originado las cordilleras submarinas de Carnegie, Cocos y Malpelo, y su producto actual, la plataforma insular de Galápagos. En este trabajo mostramos que la combinación de observaciones geofísicas, en este caso sísmicas, gravimétricas y batimétricas, permite no sólo determinar la estructura interna y propiedades físicas de la corteza, sino también restringir notablemente la naturaleza y funcionamiento del punto caliente. La estructura cortical obtenida con datos sísmicos muestra una gran uniformidad confirmando que toda la provincia es producto de un único proceso. Las variaciones laterales de densidad cortical asociadas a la presencia de las cordilleras explican las anomalías batimétricas y gravimétricas observadas, lo cual implica que el manto bajo las cordilleras submarinas es uniforme. Finalmente, se ha desarrollado un modelo 2-D de fusión del manto para ilustrar que la corteza de las cordilleras no parece ser producto de un manto anómalamente caliente, aún cuando se incluyan una fuente hidratada o tasas de ascensión rápidas. Por el contrario, una ascensión pasiva, en respuesta a la expansión oceánica, de un manto de temperatura normal, pero heterogéneo y fértil como resultado del enriquecimiento por reciclaje de corteza oceánica, explica de forma natural las observaciones geofísicas. Esta interpretación es consistente con la presencia de una anomalía de baja velocidad concentrada específicamente en el manto superior que se obtiene en los modelos de tomografía global[EN] The Galápagos Volcanic Province has resulted from the interaction between the Galápagos hotspot and the Cocos- Nazca spreading center during the last 20 m.y. This continuous interaction has produced an excess of magmatism of variable intensity that has originated the submarine aseismic ridges of Carnegie, Cocos and Malpelo, as well as its current product, the Galápagos platform. In this work, we show that the combination of geophysical observations (in this case seismic, gravity and bathymetry data) allows (1) determining the internal structure and physical properties of the lithosphere and (2) constraining the nature and functioning of the hotspot. The crustal structure modelled based on wide-angle seismic data is notably uniform, confirming that the whole province is probably the result of a single, long-standing process. The lateral variations of the crustal density associated to the presence of the aseismic ridges account for the observed gravity and bathymetry anomalies, implying that the lithospheric mantle density beneath them is uniform. We have finally developed a 2D melting model to illustrate that the crust of the different aseismic ridges does not seem to be the product of a thermal anomaly, even if we consider the presence of a hydrous mantle source or considerably active mantle upwelling. In contrast, passive upwelling of a normal temperature but fertile mantle source that may result from recycling of oceanic crust prior to melting, accounts more easily for the geophysical observations. This interpretation is consistent with the presence of a low velocity anomaly specifically concentrated in the upper mantle obtained in global tomography modelsPeer Reviewe
Structure and activity of the imbricated wedge of the Gulf of Cadiz from MCS images
No full textEuropean Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 pageIn this work we present new results on the structure and activity of the imbricated wedge of the Gulf of Cadiz based on ~ 3000 km of multichannel (MCS) profiles acquired off NW Moroccan margin. Seismic images indicates that the imbricated wedge is bounded between the Gulf of Cadiz margin at the north, the Kenitra margin at the south and the Rharb margin at the east. It is imaged as a sedimentary body with variable seismic amplitude, and structured by imbricated thrust sheets similar to an accretionary prism. Its maximum thickness is located at the east region of the gulf. It gradually thins toward the center and south of the gulf, where it is buried by ~ 0.3 twts of sedimentary deposits, indicating that the imbricated wedge is actually not growing. It probably stops it s activity at ~ 5-6 Ma. The imbricated wedge is overlaid by sedimentary sequences whose oldest unit is uppermost Tortonian. No evidences of gravitational (olistostrom) origin were founded. Active deformation related to plate convergence corresponds mainly to strike-slip faulting and minor thrusting. Mud diapirism is imaged intruding both the imbricated wedge and the overlaying sediments. At the south, the seismic images show normal faulting probably related with an extended continental crust or a continent-ocean transition crust. The age of this extension is probably Triassic-Jurassic, and we propose it as the conjugated margin of the Gulf of Cadiz. Toward the east, MCS profiles image high-amplitude continent-verging reflections corresponding to perva- sive normal faulting. These deformation related to a extended terrain, named Rharb margin, seems to act as the backstop of the imbricated wedge, and it is over-thrusted by Prebetic/Flysh sequences off the Strait of GibraltarPeer Reviewe
Structure and origin of the imbricated wedge of the Gulf of Cadiz from MCS images
No full text16TH SEISMIX International Symposium on Multi-scale Seismic Imaging of the Earth's crust and Upper Mantle, 12-17 October 2014, Castelldefels, Barcelona.-- 1 pageWe present new insights on the structure and origin of the imbricated wedge of the Gulf of Cadiz based on ~3000 km of multichannel (MCS) profiles acquired off NW Moroccan margin. Seismic images indicate that the imbricated wedge is bounded between the Gulf of Cadiz Margin (North), the Rharb Margin (East) and the Kenitra Margin (South). It is imaged as a sedimentary body, with semi-chaotic facies and variable seismic amplitude, which is structured by imbricated thrust sheets similar to an accretionary prism. This wedge thins toward the centre of the gulf, where it is buried by ~0.3 twts of sedimentary deposits, indicating that it is currently not growing. Probably it stops its activity at ~5-6 Ma. No evidences for a gravitational (olistostrom) origin have been found. The imbricated wedge is overlaid by sedimentary sequences whose oldest unit is uppermost Tortonian. Plate convergence is currently causing active faulting deformation, mainly along strike-slip faults and minor thrusting. Mud diapirism was also imaged intruding the prism and the overlaying sediments. Regarding the prism boundaries, the Kenitra Margin, located at the southernmost area of the gulf, is an extended continental or probably continent-ocean transitional crust margin that extends under the prism. The age of margin extension is probably Triassic-Jurassic, and we propose it as the conjugated margin of the Gulf of Cadiz. Off NW Moroccan margin, MCS profiles image high-amplitude continent-verging reflections corresponding to pervasive normal faulting. This extended terrain, named Rharb Margin, acts as the backstop of the wedge to the west, and it is over-thrusted by Prebetic/Flysh sequences to the east, off the Strait of Gibraltar. Plate convergence is currently causing active faulting deformation mainly along strike-slip faults and minor thrusting that internally deforms it in a diffuse manner. Also, mud diapirism was imaged intruding the imbricated wedge and the overlaying sedimentsPeer Reviewe
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