Person:
Muñoz Martín, Alfonso

First Name

Alfonso

Last Name

Muñoz Martín

URI

https://hdl.handle.net/20.500.14352/75220

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Geodinámica, Estratigrafía y Paleontología

Area

Geodinámica Interna

Identifiers

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Now showing 1 - 10 of 10

Relación entre la complejidad estructural frágil y la distribución espacial de la sismicidad en tres regímenes tectónicos diferentes (Sur de Centro América)
(Geotemas, 2000) Muñoz Martín, Alfonso; Arcila, M.; Pérez López, Raúl; Rodríguez Pascua, Miguel Angel; Vicente Muñoz, Gerardo de
Fracturation process is the main geological mechanism for earthquakes generation as well as their magnitude and spatial distribution. In this work we analyze the correlation among a geometric, cinematic and dynamic fault-slip analysis with the magnitude frequency distribution (Ms) and the epicentral setting into three different tectonic areas. In order to compare all these parameters these areas have the same surface (2°x2°) and a similar number of epicentres. The brittle structural complexity has been defined by means an index which depends on the number of active structures as well as the different type of active faults under the present-day stress tensor. The obtained results seem indicate that a bigger index of brittle structural complexity has a good relationship with an increasing of the "b" value and with a bigger complexity in the spatial distribution of earthquakes defined by the fractal dimension (capacity dimension, Dcap).
Caracterización geoeléctrica de los depósitos superficiales en la Antártida Occidental (Isla Livingstone, Islas Shetland del Sur, Antártida Occidental)
(Geogaceta, 2000) Muñoz Martín, Alfonso; Giner Robles, Jorge; González Casado, José Manuel; López Martínez, Jerónimo; Durán Valsero, Juan José; Gumiel, Pablo; Serrano, Enrique
The geophysical study of superficial deposits (mainly gravels) in ice-free areas near the seashore in the South Shetland Islands (Antarctica) allows establishing the possible existence of permafrost and buried ice bodies. In this work we have investigated the internal structure of Quaternary sediments using the resistivity method (vertical electric sounding, V.E.S.), with the purpose of establishing the resistivity values of the different materials and their geometry. We present here the results obtained from 17 vertical electric soundings carried out in Caleta Española, (north coast of Hurd Peninsula), and in the surroundings of Caleta del Glaciar Rocoso (south coast of Hurd Peninsula), both in Livingston Island. Vertical electric soundings interpretation has allowed us to characterise different units from the resistivity values (active layer, permafrost, buried ice, Quaternary deposits and their basement), and to establish the inter-phase between sea water and continental water. Moreover, with the resistivity method we have deduced the spatial distribution of some of these beds. In this way the permafrost (with resistivity values ranging between 13000 and 35000 Ω*m), and the associated active layer, is restrained to shallow depths(< 2 m) and located in the surveyed areas faraway from the seaside (i.e. mainly in the upper raised beaches). Buried ice under coarse Quaternary deposits have resistivity values of one major order magnitude than the permafrost (> 60000 Ω *m) and has been only found in the studied rock glacier.
Los corredores de fallas de Regua-Verin y Vilariça: Zonas de transferencia de la deformación intraplaca en la Península Ibérica
(Geotemas, 2004) Vegas, Ramón; Vicente Muñoz, Gerardo de; Muñoz Martín, Alfonso; Palomino, R.
A substantial part of the intraplate deformation in the Iberian Foreland is transferred from the Cantabro-Pyrenean border by means of two strike-slip deformation belts, the Regua-Verin and Vilariça fault corridors. The Neogene and recent tectonic activity along these intraplate strikeslip belts is responsible for the onset of a geomorphic barrier between the Duero Basin and the Atlantic Margin.
Reactivación intraplaca de un relieve apalachiano: Las Sierras de Guadalupe y Montánchez
(Geotemas, 2004) Álvarez, J.; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo de; Vegas, Ramón
In this work, we reconcile structural data analysis with géomorphologie observations to better constrain the morphotectonic evolution of the Guadalupe and Montánchez intraplate ranges located in western central Iberia. Fault slip data analysis and geological mapping suggest a global episode of uplift and northwest tilting during Pliocene times. The Hercynian basement was then uplifted by a NW verging thrust developing Plio-Quaternary syntectonic alluvial fans "Raña deposits". The present-day landscape of these ranges should be interpreted as a result of the interaction of (neo) tectonic forcing and longitudinal fluvial erosion.
Marco geotectónico para el noroeste de Sur América y Sur de Centro América
(Geotemas, 2000) Arcila, M.; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo de
Due to the convergence of four major plates (Nazca, South America, Cocos and Caribbean) with a group of minor blocks between Central and South America region, it is a tectonic complex area. These small plates have different relative movements respect to the main Plates. Since 1969 a group of tectonic models including different plate borders and kinematic relationships have been proposed. Nowadays there are several databases with homogeneous quality including seismicity, topography, CPS and magnetic anomalies. These databases allow building a new geotectonic model by means of the integration of all o f them. We have analyzed the topography, seismicity, actual stress regimes and plate kinematics in order to propose a new geotectonic model at the south of Central America and the northwester of South America.
Rango de Magnitudes de esfuerzos tectónicos en una zona intraplaca: el macizo de El Berrocal, borde sur del Sistema Central Español
(Geogaceta, 2002) Martín Velázquez, Silvia; Vicente Muñoz, Gerardo de; Muñoz Martín, Alfonso; Elorza Tenreiro, Francisco Javier; Vela Guzmán, Antonio
Stress magnitudes throughout a NW-SE cross-section in El Berrocal granitic massif (Spanish Central System) have been analysed by means of finite element modelling. Topographic surface, lithological differences and recent compressive tectonic stresses have been inc!uded. Two kinds of models have been performed to study the influence of rheologic properties, one with average cortical mechanical properties and the other with the main lithologies. Horizontal tectonic stress magnitudes obtained in the last model have been checked with the recent stress ratio got by stress inversion of fault slip data. Horizontal tectonic load that better fits recent tectonic stress distribution is in the range of 10-15 MPa.
Dimensión fractal de la distribución espacial de fracturas en el área granítica de el Berrocal (Sistema Central): relación con el tensor de esfuerzos
(Revista de la Sociedad Geológica de España, 2000) Pérez López, Raúl; Muñoz Martín, Alfonso; Elorza Tenreiro, Francisco Javier; Paredes Bartolomé, Carlos; Vicente Muñoz, Gerardo de
En este trabajo se ha realizado un análisis del patrón de fracturación en el macizo granítico de El Berrocal mediante un análisis fractal a tres escalas diferentes (1:2.000, 1:10.000 y 1:500.000). El análisis se realizó en primer término para todo el conjunto de fracturas cartografiadas, y posteriormente con los mapas de fracturas filtrados mediante criterios dinámicos (sólo con las fracturas potencialmente activas bajo uno de los dos campos de paleoesfuerzos deducidos). La técnica empleada en el cálculo de la dimensión fractal fue el conteo binario de celdas bidimensional (box-counting 2-D) Y unidimensional (box-counting 1-D). Con esta última técnica se ha obtenido la variación de dimensión fractal con la orientación del perfil de fracturación analizado, que evidencia la existencia de una anisotropía fractal espacial de la fracturación en el caso de los mapas de fracturas asociados a los campos de paleoesfuerzos. La variación anisótropa de la fracturación muestra una dirección de máxima complejidad en el espaciado entre fracturas, reflejada en el valor máximo de dimensión fractal que es perpendicular a la orientación del máximo esfuerzo horizontal (σHmax). Por lo que respecta a las magnitudes de la dimensión fractal, ésta es mayor en el campo de paleoesfuerzos más reciente (Alpino), lo cual concuerda con que este campo de esfuerzos reactiva fallas previas y forma nuevas fallas, resultando un patrón de fracturación más complejo, y por tanto con mayor dimensión fractal. [ABSTRACT] A fractal analysis of fracture spatial patterns was carried out in the granitic massif of "El Berrocal" for three structural map scales (1:2.000, 1:10.000 and 1:500.000). At first, the total fracture map was analysed on each scale, and a second step, the dynarnic fracture maps were built and analysed by filtering of active faults due to two stress fields. The technique used to obtain the fractal dimension was the "box-counting" l-D and 2-D (one dimension and two dimension). The "box-counting l-D" technique has been used to take values of the fractal dimension related to the orientation of the measurements. One fractal anisotropy was showed in dynamic fracture maps associated to palaeostress fields, as the maximum value of fractal dimensiono A good relationship has been found between σHmax strike (maximum horizontal stress) and the orientation of the fracturing profiles for the maximum fractal dimension value. First results point to SHmax strike is perpendicular with the maximum complexity orientation. The larger value of fractal dimension in fracture dynarnic map due to recent stress field (Alpine) is agree with the fact that, this stress field activates old faults and generates new faults, and it shows a more complex fracture pattern.
Análisis de la fracturación y campos de paleoesfuerzos en el centrooeste de la Península Ibérica.
(Geotemas, 2004) Antón López, Loreto; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo de
The Tormes Dome is a granitic massif emplaced during the Hercinian orogeny and later deformed by several posthercynian fracturation episodes. Three main paleostress fields have been obtained from stress inversion o f 1375 fault-slip data collected throughout the study area. The maximum horizontal stress (SHMAX) are oriented N-S, NE-SW and E-W with extensional and strike-slip stress regimes. Difficulties to determine age dating o f the three paleostress fields made necessary to enlarge the study area to the surrounding Cenozoic basins borders. In addition, geocronological information obtained form K-Ar dating o f fault gouges collected in the Tomes Dome has been used to establish the relative chronology of the three tectonic episodes from field data and determine their activity periods form Mesozoic to present time. An important result is that there is no relevant brittle tectonic activity associated with the recent NW-SE stress field in the western peninsula from Upper Miocene to the present times and some field evidences, as well as two focal mechanisms of earthquakes occurred in the area seem that in the Tormes Dome the recent stress field present an Shmax oriented N-S.
El cabalgamiento de Valdesotos: consecuencias de la acomodación del acortamiento cenozoico en el zócalo del Sistema Central
(Geotemas, 2004) Olaiz Campos, Antonio José; Vicente Muñoz, Gerardo de; Vegas, Ramón; González Casado, José Manuel; Muñoz Martín, Alfonso; Álvarez, J.
We describe and study structural evidences concerning to Alpine tectonics at NE sector o f the Spanish Central System (SCS). In Valdesotos area, the Hercynian basement is uplifted over Mesozoic sediments, throughout a main SW verging thrust. Fault population analysis and geological mapping has been used to look at the relation between structures in the basement and in the cover. As a consequence of accommodation of strains in the basement, kink folds are developed, such as secondary thrust and folds in the tegument. All these meso- and macrostructures seem to answer to a shortening in agreement with the Cenozoic deformation.
Características de los tensores de esfuerzos activos entre la Dorsal Centroatlántica y la Península Ibérica.
(Geotemas, 2000) Vicente Muñoz, Gerardo de; Martín Velázquez, Silvia; Rodríguez Pascua, Miguel Angel; Muñoz Martín, Alfonso; Arcila, M.; Andeweg, Bernd
The orientation of the principal stresses and the principal stress difference ratio has been determined along the southwestern boundary of the Euroasiatic plate with Northamerican and African plates by inversion method of focal mechanisms of earthquakes. The ridge push (30~ to 65Q N) ranges from E-W to ESE-WSW, with R values that show a triaxial extensional stress. The state of stress changes to strike-slip regime in the transform fault zones, and the Shmax strike turns clockwise to NW in the dextral strike-slip faults and counterclockwise to the NE in the sinistral ones. Along the margin between the Euroasiatic-African plates, from the Azores triple junction to Algeria, Shmax keeps a constant NW-SE strike but the stress ratio values range from triaxial extensional stress state, to the West, to uniaxial compresive stress state, to the East, passing through a strike-slip regime in the middle zone. In this context and with a widely NWSE Shmax, strike-slip and extensional stresses prevail in most Iberian peninsula, whereas southwards it is dominated by uniaxial compresive stresses.