Recent tectonic model for the Upper Tagus Basin (central Spain)

Abstract

Active tectonics within the Upper Tagus Basin is related to the lithospheric flexure affecting the Palaeozoic basement of the basin. This flexure displays NE-SW trending. Besides, this structure is in agreement with the regional active stress field defined by the maximum horizontal stress with NW-SE trending. In this tectonic framework, irregular clusters of instrumental seismicity (Mw< 5.0) fade in the zone bounded by the Tagus River and the Jarama River valleys. These clusters are related to major NW-SE trending faults of suspected strike-slip kinematics. Moreover, reverse faults with NE-SW trending are affected by the strike-slip system as well. Despite the reverse faults are in agreement with the present SHMAX orientation, though, they apparently are blocked as seismogenic sources (scarce instrumental seismicity recorded today). In addition, we have determined the regional and local stress/ strain fields and two different fracture patterns were observed. Hence, we have divided the area in two zones: (1) the lateral bands of the basin, defined by reverse faulting (NE-SW trending) and strike-slip faulting (NW-SE trending) and (2) the central zone of the basin characterized by shallow normal faulting and NE-SW trending strike-slip faults. Furthermore, surface faulting and liquefaction structures are described affecting Middle to Late Pleistocene fluvial deposits, suggesting intrabasinal palaeoseismic activity (5.5 < M < 6.5) during the Late Quaternary. The obtained structural and tectonic information has been used to classify and characterize the Upper Tagus Basin as a semi-stable intraplate seismogenic zone, featured by Pleistocene slip-rates < 0.02 mm/yr. This value is low but it affords the occurrence of Pleistocene paleoearthquakes.

Crustal Imbrication in an Alpine Intraplate Mountain Range: A Wide‐Angle Cross‐Section Across the Spanish‐Portuguese Central System

“…Furthermore, in the Madrid Cenozoic basin and south of the Guadarrama sector, recent and historical seismicity (Rodríguez‐Pascua et al., 2016) is explained by Giner‐Robles et al. (2012) as: (a) tectonic far‐field stress of plate convergence, (b) lithospheric flexion evidenced by large basement wave‐length folding, and (c) the tectonic loading associated with the topography of the SPCS. We therefore suggest that the exhumation of the SPCS by south‐directed thick‐skinned thrusts may be related to the underthrusting of the basement south of the SPCS and be one of the mechanisms responsible for the difference in altitude in both foreland basins influenced by their different erosional history (de Vicente & Muñoz‐Martín, 2013).…”

Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

“…The topography of the mountains and the basements of the bordering basins, as well as the present-day crustal and lithospheric structure, are maintained by large-scale folding and crustal thickening (Martín-Velázquez and De Vicente, 2012). Quaternary palaeoseismic structures have been recognised in the Madrid Basin (Rodríguez-Pascua 2005;Giner-Robles et al, 2012) but the seismicity is moderate to low and it is restricted to a depth of ~15 km Herraiz et al, 2000;Tejero and Ruiz, 2002;De Vicente et al, 2007, 2008Giner-Robles et al, 2012). In the Iberian Peninsula, the active tectonic regime changes from a thrustfault regime in its SW corner to a normal-fault regime in its NE corner (Jiménez-Munt and Negredo, 2003;Olaiz et al, 2009).…”

“…crustal seismicity (Sibson, 1986;Zoback and Townend, 2001;Watts and Burov, 2003;Aldersons et al, 2003). Seismicity in the interior of Iberia is low to moderate Andeweg et al, 1999;Herraiz et al, 2000;Tejero and Ruiz, 2002;De Vicente et al, 2007, 2008Giner-Robles et al, 2012). Seisms concentrate toward the SE of the Madrid Basin, owing to a flexural forebulge, and in basement faults at the southern edge of the Central System (Fig.…”

“…Seisms concentrate toward the SE of the Madrid Basin, owing to a flexural forebulge, and in basement faults at the southern edge of the Central System (Fig. 7a) Andeweg et al, 1999;De Vicente et al, 2007;Giner-Robles et al, 2012).…”

“…1) (Vegas et al 1990;De Vicente et al 2007). The stress regime is complex and seismicity is low to moderate Herraiz et al 2000;De Vicente et al 2007;Giner-Robles et al 2012). Several studies have addressed the estimate of lithospheric strength to explain these characteristics (Van Wees et al, 1996;Gómez-Ortiz 2001;Tejero and Ruiz 2002;Gómez-Ortiz et al, 2005b;Pérez-Gussinyé and Watts 2005;Jiménez-Díaz et al, 2012).…”