Publication: Estado de esfuerzos actual en la Cordillera Bética Oriental
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2001
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Instituto Geológico y Minero de España
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Abstract
La zona estudiada se sitúa en el sureste de la Península Ibérica abarcando esencialmente la Cordillera Bética Oriental, en la que se ha calculado el campo de esfuerzos actuales mediante el análisis de la sismicidad. El área elegida para la selección de terremotos corresponde a las coordenadas: 0° y -4° de longitud y 40° y 37° de latitud. Para el cálculo conjunto de los mecanismos focales se ha utilizado la metodología propuesta por Giner (1996): Cálculo Poblacional Ponderado de los Mecanismos Focales de Terremotos. Con este método se han calculado 28 mecanismos focales de los que se obtienen dos direcciones de máximo acortamiento en la horizontal (sHMAX ): NO-SE y NESO. La dirección NO-SE está definida por fallas inversas, mientras que la NE-SO por fallas normales. Las fallas normales tienden a ser más superficiales que las inversas, lo que se ha interpretado como consecuencia de una flexura cortical de dirección NE-SO. Es decir, las fallas inversas se generan por debajo de la superficie neutra de esta flexura antiformal (donde hay compresión) y las normales por encima (donde hay extensión). La flexura está generada por el choque de la Placa Africana con la Península Ibérica (Placa Eurasiática), responsable de la formación de la Cordillera Bética, con una dirección de acercamiento general NO-SE, coincidente con el campo de esfuerzos calculado. La dirección NE-SO corresponde a un campo secundario generado por los efectos de extensión superficiales producidos por la flexura antiformal.
The study area is located in the Eastern Betic Chain (Southeastern Iberian Peninsula), in which the stress field has been calculated by seismic analysis. The selected earthquakes are situated between 0° and -4° of longitude and between 40° and 37° of latitude. For earthquake focal mechanisms Population Calculation (Giner´s methodology, 1996) has been used: Pondered Population Calculation of Earthquake Focal Mechanisms. 28 earthquake focal mechanisms have been calculated and two orientations of maximum horizontal stress (sHMAX) have been obtained: NW-SE and NE-SW. The NW-SE orientation is defined by reverse faults, while the NE-SW is defined by normal faults. The normal faults are more surficial than the reverse ones, which has been interpreted by NE-SW flexural bending of the Betic Chain. According, reverse faults are generated below neutral surface of flexural bending (where compression exists) and the normal ones are generated above that surface (where extension exists). The flexural bending is generated by collision of the African Plate against the Iberian Peninsula (Eurasian Plate), with an approximate NW-SE orientation, coincident with the calculated NW-SE stress field. The NE-SW orientation corresponds to a secondary stress field generated by surficial extension that takes place over the antiformal flexure bending.
The study area is located in the Eastern Betic Chain (Southeastern Iberian Peninsula), in which the stress field has been calculated by seismic analysis. The selected earthquakes are situated between 0° and -4° of longitude and between 40° and 37° of latitude. For earthquake focal mechanisms Population Calculation (Giner´s methodology, 1996) has been used: Pondered Population Calculation of Earthquake Focal Mechanisms. 28 earthquake focal mechanisms have been calculated and two orientations of maximum horizontal stress (sHMAX) have been obtained: NW-SE and NE-SW. The NW-SE orientation is defined by reverse faults, while the NE-SW is defined by normal faults. The normal faults are more surficial than the reverse ones, which has been interpreted by NE-SW flexural bending of the Betic Chain. According, reverse faults are generated below neutral surface of flexural bending (where compression exists) and the normal ones are generated above that surface (where extension exists). The flexural bending is generated by collision of the African Plate against the Iberian Peninsula (Eurasian Plate), with an approximate NW-SE orientation, coincident with the calculated NW-SE stress field. The NE-SW orientation corresponds to a secondary stress field generated by surficial extension that takes place over the antiformal flexure bending.