The recent (upper Miocene to Quaternary) and present tectonic stress distributions in the Iberian Peninsula (original) (raw)
Related papers
Journal of Geophysical Research, 1992
By means of fault population analysis (using the right dihedra, y-R diagram and Etchecopar's methods), the states of stress in a number of sites of the Cameros Massff (Northwestern Iberian Chain, Spain) and nearby areas of the Ebro Basin have been determined. These states of stress have been used as a framework in order to infer a model of the actual stress field in that area during the main stage of the Alpine compression (Oligocene-lower Miocene). The three main compression directions obtained (NW-SE, NNE, NE-SW)can be explained by a single compression field with horizontal o, trending NNE and vertical 02, whose primary trajectories are deflected due to (1) largescale strike-slip faults or lateral ramps of thrusts or (2) frontal ramps of thrusts oblique to the main compressire axis. The reliability of this scheme has been checked by means of a two-dimensional mathematical model based upon the finite element method and applied on a sheet whose theological properties are similar to those of a standard limestone. This model simulates the main features of the regional stress field, and it was constructed after determining the average parameters of the possible external or "primary" field and simulating the major faults that could deflect the stress trajectories. INTRODUCTION Palaeostresses can be determined by means of analysis of fault populations on an outcrop scale. Several methods for this kind of analysis have been performed in the last l0 years [
Palaeogene evolution of deformation in the northeastern Iberian Peninsula
Geological Magazine, 1984
During the Palaeogene Alpine compression three units were differentiated in the studied area (south of the Ebro Basin): the Catalan Coastal Range, dominated by NE-SW major basement faults with a sinistral movement; The Iberian Range, where the important basement faults have a NW-SE direction and a reverse movement (often with a dextral component); the Linking Zone, between these two ranges, where an E-W dominant structural direction is marked by an array of folds and thrusts (with a northward vergence) in the Mesozoic cover.
Seismicity and potencially active faults in the Northwest and Central-West Iberian Peninsula
Journal of Iberian Geology, 2012
7KH 1RUWKZHVW DQG &HQWUDO:HVW ,EHULDQ 3HQLQVXOD FRQ¿JXUH DQ LQWUDSODWH DUHD IDU IURP WKH DFWLYH SODWH ERXQGDULHV ZKHUH WKH Variscan basement crops out extensively (Iberian Massif). This area of the Iberian Peninsula has been traditionally considered a seismically stable region; however, it presents a moderate intraplate seismicity which indicates the presence of active structures and WKH RFFXUUHQFH RI SRWHQWLDOO\ GDPDJLQJ HDUWKTXDNHV 7KH VFDUFLW\ RI 0HVR]RLF DQG &HQR]RLF GHSRVLWV PDNHV YHU\ GLI¿FXOW WR WUDFN the record of the more recent tectonic activity and the characterization of active tectonic structures within the Iberian Massif. Nevertheless the seismic sequences of 1995-1997 in Lugo (5.1 mb; IV) and 2003 in Zamora (4.2 Mw) provided important information about the orientation of the present stress tensor, and the distribution of the hypocenters informed about the rupture geometry of WKH IDXOW SODQHV 7KH SUHVHQW ZRUN LQWHJUDWHV JHRORJLFDO JHRPRUSKRORJLFDO VWUXFWXUDO DQG VHLVPRORJLFDO GDWD LQ RUGHU WR GH¿QH WKH main potentially active faults in the region. Faults trending NE-SW to N-S are potentially active as strike-slip, in some cases with a reverse component, under a NW-SE to N-S compression.
Journal of Iberian Geology, 2012
7KH 1RUWKZHVW DQG &HQWUDO:HVW ,EHULDQ 3HQLQVXOD FRQ¿JXUH DQ LQWUDSODWH DUHD IDU IURP WKH DFWLYH SODWH ERXQGDULHV ZKHUH WKH Variscan basement crops out extensively (Iberian Massif). This area of the Iberian Peninsula has been traditionally considered a seismically stable region; however, it presents a moderate intraplate seismicity which indicates the presence of active structures and WKH RFFXUUHQFH RI SRWHQWLDOO\ GDPDJLQJ HDUWKTXDNHV 7KH VFDUFLW\ RI 0HVR]RLF DQG &HQR]RLF GHSRVLWV PDNHV YHU\ GLI¿FXOW WR WUDFN the record of the more recent tectonic activity and the characterization of active tectonic structures within the Iberian Massif. Nevertheless the seismic sequences of 1995-1997 in Lugo (5.1 mb; IV) and 2003 in Zamora (4.2 Mw) provided important information about the orientation of the present stress tensor, and the distribution of the hypocenters informed about the rupture geometry of WKH IDXOW SODQHV 7KH SUHVHQW ZRUN LQWHJUDWHV JHRORJLFDO JHRPRUSKRORJLFDO VWUXFWXUDO DQG VHLVPRORJLFDO GDWD LQ RUGHU WR GH¿QH WKH main potentially active faults in the region. Faults trending NE-SW to N-S are potentially active as strike-slip, in some cases with a reverse component, under a NW-SE to N-S compression.
Geomorphology, 2006
The landscape of today's central Iberian Peninsula has been shaped by ongoing tectonic activity since the Tertiary. This landscape comprises a mountain ridge trending E-W to NW-SE, the Central System, separating two regions of smooth topography: the basins of the rivers Duero and Tajo. In this study, we explore interrelationships between topography and tectonics in the central Iberian Peninsula. Regional landscape features were analysed using a digital elevation model (DEM). Slope gradients and slope orientations derived from the DEM were combined to describe topographic surface roughness. Topography trendsurfaces inferred from harmonic analysis were used to define regional topographic features. Low roughness emphasizes the smooth nature of the basins' topography, where surfaces of homogeneous slope gradient and orientation dominate. High roughness was associated with abrupt changes in gradient and slope orientation such as those affecting crests, valley bottoms and scarp edges present in the mountain chain and in some deep incised valleys in the basins. One of the applications of roughness mapping was its capacity to isolate incised valley segments. The area distribution of incised rivers shows their prevalence in the east. On a regional scale, the topographic surface can be described as a train of NE-SW undulations or waves of 20 km wavelength. These undulations undergo changes in direction and interruptions limited by N-S-trending breaks. E-W and NE-SW troughs and ridges clearly mark structural uplifts and depressions within the Central System. These structures are transverse to the compressive NW-SE stress field that controlled the deformation of the central Iberian Peninsula from the Neogene to the present. They represent the upper crustal folding that accommodates Alpine shortening. N-S breaks coincide with Late Miocene faults that control the basins' sedimentation. Further, associated palaeoseismic structures suggest the recent tectonic activity of N-S faults in the eastern part of the Tajo Basin. Apatite fission track analysis data for this area suggest the occurrence of a significant uplift episode from 7 to 10 Ma which induced the river incisions appearing in the roughness map. N-S and NE-SW faults could be seismogenic sources for the current moderate to low seismic activity of the east Tajo Basin and southeast Central System. Although N-S fault activity has already been established, we propose its significant contribution to shaping the landscape. D
Analysis of a gradual change in stress regime (example from the Eastern Iberian Chain, Spain
Tectonophysics, 1986
Simon Gomez, J.L., 1986. Analysis of a gradual change in stress regime (example from the eastern lberian Chain, Spain). Tectonophysics. 124: 31-53. The compression-extension passage in the eastern Iberian Chain during the Miocene is analyzed; structural data suggest that it is a gradual change in stress regime which does not involve rotation but interchange of CI, and o2 axes, one of them remaining always vertical. The gradual stress evolution is interpreted by a numerical-graphic method (y-R diagram) which optimizes combinations of y (azimuth of the maximum horizontal axis) and R (stress ratio) explaining groups of fault movements. The y-R diagrams of some fault populations measured in the Castellon region provide optimum tensors appearing within a continuous cloud of solutions from the compressional field to the extensional one. Movement sequences obtained from superimposed striations indicate a systematic stress change between these two regimes.
Tectonophysics, 1996
A brittle deformation tectonic analysis was performed in central Spain (Spanish Central System and Madrid Basin) in order to decipher and understand the deformation processes that take place in a typical intracontinental zone. 1174 fault slickensides obtained in materials with ages between Late Cretaceous and Quaternary have been analyzed by means of fault population analysis methods to reconstruct paleostress tensors. Nine earthquake focal mechanisms have been determined, with magnitudes ranging between 3 and 4.1.With regard to regional structural features and sedimentary record data, the characteristics of present-day and neotectonic stress fields have been figured out, which determine the neotectonic period for this region.Thus, we have established that the intraplate zone represented by central Spain has been subjected to a stress field from the Middle Miocene until the present-day with a largest horizontal shortening direction (SHMAX) located between N130E and N160E.Finally, three paleostress maps with the main active structures are presented for: (a) Middle Miocene to Late Miocene, the period when the Spanish Central System was mainly formed, (b) Late Miocene to Quaternary, and (c) the present-day stress field, deduced from earthquake focal mechanisms.
Tectonophysics, 1999
Tertiary to present deformation in the interior of the Iberian Peninsula reflects spatial and temporal variations of the activity of the plate boundaries. Local deformation patterns observed in many of the numerous intraplate Tertiary basins and their borders, such as the Madrid Basin and the Sierra de Altomira, are at first sight incompatible with the regional stress field under which they were formed. We demonstrate, however, that they can be explained as the effect of several stress fields that acted on the Iberian Peninsula from earliest Tertiary onward. Data on local deformation can constrain both magnitudes and directions of forces acting on the plate boundaries of Iberia, enabling us to estimate the relative importance of the different plate driving and deforming mechanisms providing further constraints on the tectonic evolution of Iberia.
Stress fields in the Iberian-Maghrebi region
Journal of Seismology, 2003
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.