Stress fields in the Iberian-Maghrebi region |
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| Authors: | J Henares C López Casado C Sanz de Galdeano J Delgado JA Peláez |
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| Institution: | (1) Dpto. Física Teórica y del Cosmos, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain;(2) Instituto Andaluz de Ciencias de la Tierra (CSIC-Univ. Granada), Facultad de Ciencias, 18071 Granada, Spain;(3) Dpto. Ciencias de la Tierra, Universidad de Alicante, Ap. Correos 99, 03080 Alicante, Spain, tel;(4) Dpto. Física, Escuela Politécnica Superior, Universidad de Jaén, 23071 Jaén, Spain |
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| Abstract: | This study concerns the present stressfield between the Eurasian and Africanplates in the Iberian-Maghrebi region(Portugal, Spain, Morocco, Algeria andTunisia). In addition to an up-to-datecatalogue of earthquakes in this area, acatalogue of the focal mechanisms composedof 486 solutions of fault planes,standardized in terms of notation andinformation type, was used. These data wereused applying the right-dihedron method ofAngelier and Mechler (1977), to obtaindifferent zones with homogeneous stress.The results obtained for shallowearthquakes (h < 30 km) coincide, in themajority of cases, with the general stressfields proposed by numerous authors forthis region, according to which there isNW-SE compression. However, the stressorientation appears to vary in certainareas, perhaps perturbed by the opening ofthe Atlantic Ocean, the approach of Iberiaand Africa, or the extension of the AlboranSea.For the intermediate earthquakes (30 < h< 150 km) no general pattern was found,and the P and T axes seem to be randomlyoriented for the depth intervalsconsidered. For the very deep earthquakes(h > 600 km), however, the P axis lies ina NNW-SSE direction, dipping towards theSSE, while the T axis is subhorizontal in aNE-SW direction.The determinations from the focalmechanisms highlight the existence of aregional stress field with a subhorizontalcompression axis trending NW-SE. Superimposed are others that specificallyaffect particular sectors; these arerelated to the opening of the AtlanticOcean, the extension of the BeticCordillera and the Alboran Sea, and eventhe present compression between the Iberianand European plates. |
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| Keywords: | Betic Cordillera Iberian-Maghrebi region focal mechanism present-day stress field |
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