Publication: Estado de esfuerzos en la Corteza a partir del estudio de mecanismos focales
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2016-06-24
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Universidad Complutense de Madrid
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Abstract
La presente Tesis Doctoral lleva por título Estado de esfuerzos en la Corteza a partir del análisis de mecanismos focales. La determinación del estado de esfuerzos es un aspecto muy importante en varios aspectos de la sociedad y su estudio se ha abordado desde distintos parámetros en los últimos años. Los mecanismos focales son los datos más fiables para conocer el estado de esfuerzos en la corteza, ya que cubren el rango completo de profundidades de la propia corteza y registran eventos en cualquier punto del planeta. De Vicente (1988) desarrolla el Modelo de Deslizamiento originalmente para el análisis de paleoesfuerzos a partir de estructuras frágiles y posteriormente se ha aplicado a mecanismos focales (Capote et al., 1991). Esta metodología permite calcular de forma independiente para cada mecanismo focal la dirección de máximo acortamiento en la horizontal (Dey) y el régimen de esfuerzo-deformación definido por el factor de forma (ḱ), que es la relación entre la deformación en la vertical y la horizontal. A partir de estos datos puntuales se generan mapas continuos en distintas regiones, que se desarrollan en cada uno de los capítulos que componen esta Tesis Doctoral. El análisis del catálogo del Centroid Moment Tensor permite estudiar de forma global la distribución de esfuerzos en la Corteza. Éstos están principalmente controlados por las fuerzas originadas en los límites primarios de placas y se transmiten de forma continua a lo largo de cientos de kilómetros, que sufren perturbaciones a escala regional o local, asociadas a distintas estructuras geológicas. Además se observa que en las zonas intraplaca domina el régimen tipo desgarre, quedando los máximos compresivos y extensionales localizados principalmente a las zonas de subducción y de dorsal o rift respectivamente. Además el análisis estadístico del catálogo revela que la mayor parte de los terremotos que se generan en la Corteza se caracterizan por ser de deformación casi pura, es decir con ángulos de cabeceo y/o buzamiento próximos a 0° o a 90°, que es la forma más eficiente de disipar la energía...
This PhD Thesis is titled Stress conditions in the Crust from focal mechanisms analysis. Stress condition is a very important aspect for the global community. During the last decades many studies has been carried out trying to stablish the origin of the stresses. Focal mechanisms are the most accurate data for this type of analysis, because they can be located at any depth within the crust and their coverage is global. De Vicente (1988) published the Slip Model originally developed for paleostress analysis, using brittle structures and later applied to focal mechanisms (Capote et al., 1991). This methodology allows to calculate the maximum shortening direction (Dey) and the strainstress regime defined by the ḱ ratio or shape factor (ey/ez, horizontal maximum/vertical strain), in an independent way for each focal mechanism This data set is interpolated, generating continuous maps of stress-strain regime and Dey, which has been developed and explained in every chapter. The detailed review of the Centroid Moment Tensor catalogue enables the stress characterization worldwide. Stresses are generated at major plate boundaries and are transmitted through the lithosphere for hundreds of kilometers. Due to geological features stresses can be perturbed regionally or locally. Intraplate stresses are defined by strike-slip regime, while compressive and extensional areas are mainly related to subduction and ridge zones respectively. Statistical analysis reveals that the majority of the earthquakes are near to pure deformation, represented by values of pitch and dip close to 0º or 90º, which is the most efficient way to dissipate energy...
This PhD Thesis is titled Stress conditions in the Crust from focal mechanisms analysis. Stress condition is a very important aspect for the global community. During the last decades many studies has been carried out trying to stablish the origin of the stresses. Focal mechanisms are the most accurate data for this type of analysis, because they can be located at any depth within the crust and their coverage is global. De Vicente (1988) published the Slip Model originally developed for paleostress analysis, using brittle structures and later applied to focal mechanisms (Capote et al., 1991). This methodology allows to calculate the maximum shortening direction (Dey) and the strainstress regime defined by the ḱ ratio or shape factor (ey/ez, horizontal maximum/vertical strain), in an independent way for each focal mechanism This data set is interpolated, generating continuous maps of stress-strain regime and Dey, which has been developed and explained in every chapter. The detailed review of the Centroid Moment Tensor catalogue enables the stress characterization worldwide. Stresses are generated at major plate boundaries and are transmitted through the lithosphere for hundreds of kilometers. Due to geological features stresses can be perturbed regionally or locally. Intraplate stresses are defined by strike-slip regime, while compressive and extensional areas are mainly related to subduction and ridge zones respectively. Statistical analysis reveals that the majority of the earthquakes are near to pure deformation, represented by values of pitch and dip close to 0º or 90º, which is the most efficient way to dissipate energy...
Description
Tesis inédita presentada en la Universidad Complutense de Madrid, Facultad de Ciencias Geológicas, Departamento de Geodinámica, leída el 20-01-2016