Person:
Muñoz Martín, Alfonso

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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
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Author: Pérez López, Raúl × Start date: 1994 ×

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Now showing 1 - 3 of 3
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    Relationship between the fractal dimension anisotropy of the spatial faults distribution and the paleostress fields on a Variscan granitic massif (Central Spain): the F-parameter
    (Journal of Structural Geology, 2005) Pérez López, Raúl; Paredes, Carlos; Muñoz Martín, Alfonso
    The spatial distribution of faults is usually described as a fractal set characterised by the fractal dimension. In this work, we have filtered fault patterns interpreted from digital elevation models, aerial photographs and field maps, by using structural geological parameters of the stress ellipsoid (stress tensor direction and stress ratio R0) and age of deformation. From these filtered structural maps, we have obtained the fractal dimension associated with the fracture patterns developed during Permo-Triassic and Alpine tectonic events on a Variscan granitic massif located in the Spanish Central System. Oriented fractal dimensions were calculated on several transects crossing the fault-filtered maps. The fractal dimension (D), calculated by 1-D box-counting, describes an ellipse on a polar plot with the short axis as the minimum value (DHmin) and the long axis as the maximum value (DHmax) of the fractal dimensions measured. From these analyses, we have defined the F-parameter as a function of the maximum value, minimum value and vertical value of fractal dimension (Dz), FZ(DzKDHmin)/(DHmaxK DHmin). Finally we have established, from a local scale analysis, a perpendicular relationship between the principal axes of the ellipse of the fractal spatial anisotropy of fractures and the principal axes of the stress tensor (sHmax, sHmin and sz) that generates this dynamic pattern of fractures. Furthermore, the F-parameter and the stress ratio R0 are equivalents and, applied in this area, both show a triaxial extension.
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    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.
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    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).