Person: Muñoz Martín, Alfonso
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First Name
Alfonso
Last Name
Muñoz Martín
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Geodinámica Interna
Identifiers
7 results
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Now showing 1 - 7 of 7
Item Sobre el origen de la asimetría en el patrón general del relieve en el interior de la Península Ibérica: nuevos resultados obtenidos mediante modelación análoga(Geogaceta, 2010) Fernández Lozano, Javier; Sokoutis, Dimitrios; Willingshofer, Ernst; Muñoz Martín, Alfonso; De Vicente Muñoz, Gerardo; Cloetingh, SierdAnalogue modelling contributes to the interpretation of lithosphere scale folds in Iberia as a result of largescale convergence during Oligocene-Miocene times between the Iberian and European Plates. Different tectonothermal events affected the microplate since late Paleozoic and resulted in lateral strength variations of the Iberian lithosphere. An old and cold lithosphere, Variscan in age, can be found in the westernmost part of Iberia whereas a relative weak and hot Mesozoic lithosphere affected by episodes of rifting and basin inversion during Mesozoic- Tertiary times covers the area of the Iberian Chain. Our study aims at deciphering whether deformation and topography evolution in Iberia are related to lateral strength variations and/or the inherited structural grain stemming from Variscan deformation. We also have studied the strength of the lithosphere to gain insights into the effects of rheological variations related to local thrusting or primary strength variations along the Iberian lithosphere.Item Aplicación del método de resistividades con SEV para la caracterización hidrogeológica de la cuenca de Dajla (Argelia)(Geogaceta, 2010) Torres López, Sara; Muñoz Martín, Alfonso; Jiménez Díaz, Alberto; Ahmed, Baba; De lorenzo, Javier; García López, Cristina; Olaiz Campos, Antonio JoséThe aim of this study is the hydrogeological exploration and characterization using Geophisical surveying in the vicinity of Dakhla Basin (Algeria). To that end, it has been used the method of resistivities through Vertical Electric Sounding (VES) on a campaign carried out in April 2009. The work included 19 VES, which have been calibrated with existing wells and with field geological observations. The results have allowed the characterization of Tertiary deposits as well as Ordovician sandstones. With these data, it has been possible to identify the position and thickness of a shallow salty aquifer, and the roof of a deep freshwater aquifer developed on the Ordovician sandstones. The integration of the geometry of the aquifers with the resistivity values obtained in the Ordovician sandstones has allowed the location of a favorable area for the situation of a new well.Item Gravity modeling of the Muertos Trough and tectonic implications (north-eastern Caribbean)(Marine Geophysical researches, 2010) Granja Bruña, José Luis; Muñoz Martín, Alfonso; Ten Brink, Uri S.; Carbó Gorosabel, Andrés; Llanes Estrada, Pilar; Martín Dávila, José; Córdoba Barba, Diego; Catalán, ManuelThe Muertos Trough in the northeast Caribbean has been interpreted as a subduction zone from seismicity, leading to infer a possible reversal subduction polarity. However, the distribution of the seismicity is very diffuse and makes definition of the plate geometry difficult. In addition, the compressive deformational features observed in the upper crust and sandbox kinematic modeling do not necessarily suggest a subduction process. We tested the hypothesized subduction of the Caribbean plate’s interior beneath the eastern Greater Antilles island arc using gravity modeling. Gravity models simulating a subduction process yield a regional mass deficit beneath the island arc independently of the geometry and depth of the subducted slab used in the models. This mass deficit results from sinking of the less dense Caribbean slab beneath the lithospheric mantle replacing denser mantle materials and suggests that there is not a subducted Caribbean plateau beneath the island arc. The geologically more realistic gravity model which would explain the N–S shortening observed in the upper crust requires an overthrusted Caribbean slab extending at least 60 km northward from the deformation front, a progressive increase in the thrusting angle from 8 to 30 reaching a maximum depth of 22 km beneath the insular slope. This new tectonic model for the Muertos Margin, defined as a retroarc thrusting, will help to assess the seismic and tsunami hazard in the region. The use of gravity modeling has provided targets for future wide-angle seismic surveys in the Muertos Margin.Item Análisis de esfuerzos tectónicos. Fallas y sismos(Reduca. Geología, 2010) Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo DeLa Tectónica de Placas implica una continua deformación de la Litosfera (y de la corteza superior frágil). Esta dinámica produce un campo de esfuerzos tectónicos íntimamente ligado a las estructuras activas que generan sismicidad: las fallas. El proceso de fracturación puede analizarse desde distintas perspectivas: Mecánica de Rocas, Sismología, Geología Estructural, modelado (análogo y numérico), etc. En estos apuntes abordamos el estudio del estado de esfuerzos tectónicos (activos o paleoesfuerzos), a partir del análisis de fallas desde las distintas ideas complementarias que aportan estas disciplinas. Comenzamos con una breve descripción del origen de los esfuerzos tectónicos para abordar después los conceptos mecánicos básicos, comenzando con la definición y propiedades del tensor de esfuerzos. Continuamos con el análisis de la rotura en roca intacta (fricción interna) y en roca previamente fracturada (fricción al deslizamiento). Seguidamente exponemos las ideas fundamentales que aporta la Geofísica (Sismología), comenzando con la descripción de las ondas sísmicas y terminando con el mecanismo focal de los terremotos. Acto seguido, analizamos las relaciones entre los mecanismos focales y las fallas para describir después lo que puede aportar la Geología Estructural desde el análisis de las microestructuras frágiles (estrías, venas, estilolitos). Todos estos conceptos convergen al final en el apartado de "Análisis de poblaciones de fallas y métodos de obtención del tensor de esfuerzos", donde se exponen tres métodos de inversión (Diedros rectos, Modelo de Deslizamiento y ecuación de Bott). Por último, se analiza como ejemplo el estado de esfuerzos tectónicos activos entre la Dorsal de Terceira, Iberia y Argelia, con especial atención a la Península Ibérica.Item Exploring active tectonics in the Dominican Republic(Eos, Transactions American Geophysical Union, 2010) Carbó Gorosabel, Andrés; Córdoba Barba, Diego; Martín Dávila, José; Granja Bruña, José Luis; Llanes Estrada, Pilar; Muñoz Martín, Alfonso; Ten Brink, Uri S.One recent project, Caribbean–North American Plate Boundary Analysis: From Beata Ridge (Dominican Republic) to Anegada Passage (Lesser Antilles) (CARIBENORTE), has conducted onshore and offshore surveys in the Dominican Republic region to study subduction, strike- slip, and collision processes in this area. This survey included a cruise aboard the Spanish R/V Hespérides in April 2009 and simultaneous fieldwork onshore. The CARIBE NORTE project complements the study of the northeastern Caribbean plate boundary carried out during the Structure and Geodynamics of the Northeastern Boundary of the Caribbean Plate: Puerto Rico (GEOPRICO- DO) project in 2005 [Carbó et al., 2005].Item Spectral analysis of the gravity and elevation along the western Africa–Eurasia plate tectonic limit: Continental versus oceanic lithospheric folding signals(Tectonophysics, 2010) Muñoz Martín, Alfonso; De Vicente Muñoz, Gerardo; Fernández Lozano, Javier; Cloetingh, Sierd; Willingshofer, Ernst; Sokoutis, Dimitrios; Beekman, FredLarge-scale folding is a key mechanism of lithospheric deformation and has been described in many parts of the Earth, both for the continental and oceanic lithospheres. Some aspects of this process such as the presence of coupling/decoupling between the crustal deformation and the mantle lithosphere, or between different lithospheres, make it necessary to accurately control the periodic characteristics of the elevation and of the gravity signal. 1D spectral analysis of gravity and topography profiles is sensitive to a series of factors: the location, length and orientation of the profiles, as well as the number of samples taken. We carry out a systematic analysis of the periodicities in the topography and gravity, both 1D and 2D, along the western border of the Africa–Eurasia plate tectonic boundary. We analyze the sensitivity of the 1D and 2D spectral analysis in order to compare the results along a plate boundary where oceanic and continental lithospheres are in contact with different tectonic, kinematic and rheological aspects. Our 1D spectral results indicate that the greater the profile length, the longer the wavelength peaks that are found. Nevertheless there are some periodic signals that appear in almost all the analyzed profiles: 100–250 km for the N–S profiles across oceanic plate boundary and 150–250 km where the plate boundary is developed over continental lithospheres. The 2D spectral analysis avoids the problems found in relation to the particular location of the profile but the resulting wavelengths are slightly higher than those obtained from the 1D spectral analysis. The wavelengths estimated for both oceanic and continental lithospheres at the Africa–Eurasia boundary (N250 km) show low values of mean mantle strength (b1013 Pa m). he presence of lithospheric folds means that the continental and oceanic lithospheres are mechanically oupled. This had previously been suggested for Iberia but not for the limit between S Iberia and the Terceira riple Junction. The orientation of the lithospheric folds is NW–SE at the contact between continental lithospheres and NNE–SSW at the contact between oceanic lithospheres. This difference is also reflected in the signal anisotropy and must be related to the rotation of the tectonic stresses in the same direction. A large periodic signal (wavelength N600 km) was also detected both in 1D and 2D spectral results. After drawing the filtered values, the resulting maps indicate that this signal is related to the transition between continental and oceanic lithospheres and to the significant changes in crustal and/or lithospheric thickness from the Mid-Atlantic Ridge to the continental margins of western Eurasia.Item Alpine paleostress reconstruction and active faulting in western Iberia(Central European Journal of Geosciences, 2010) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo deThe study of intraplate tectonics is crucial for understanding the deformation within plates, far from active plate boundaries and associated stress transmission to the plate interiors. This paper examines the tectonic evolution of the Variscan basement at the western margin of the Cenozoic Duero basin. Located east of the Vilariça Fault System in NW Iberia, this intraplate zone is a relatively flat but elevated area with an intense NNE-SSW trending fault system and associated moderate seismicity. Although the area has played an important role in the Duero basin configuration, its Alpine to present-day tectonic evolution has not been well constrained. In order to characterize the successive paleostress fields, 1428 pairs of fault-striae were measured at 56 sites and two focal mechanisms were used. Stress inversion methods have been applied to analyze paleostress regimes. Results show the existence of three dominant maximum horizontal stress (Shmax) trends: N-S, NE-SW and E-W. Relative and absolute dating of the activated faults for each Shmax shows that the clearly predominant N-S paleostress field in the zone has been active since the Oligocene up to the present day; while a NE-SW stress field is found to have been active during the Cretaceous and an older E-W paleostress field was active in the earlier Alpine cycle (Late Triassic).