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
4 results
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Item 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 deFracturation 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).Item Marco geotectónico para el noroeste de Sur América y Sur de Centro América(Geotemas, 2000) Arcila, M.; Muñoz Martín, Alfonso; Vicente Muñoz, Gerardo deDue 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.Item 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 deEn 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.Item 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, BerndThe 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.