“…This contrasts markedly the generally accepted picture of N-S extension in this part of the Eurasian Plate (e.g. Kotzev et al 2008;Olaiz et al 2009). It suggests that extension can be interrupted periodically by short-lived episodes of crustal stress inversion.…”
Abstract:The EU-TecNet monitoring network uses customized three-dimensional extensometers to record transient deformations across individual faults. This paper presents the first results from two newly established monitoring points in the Balkan Mountains in Bulgaria. The data from Saeva Dupka, recorded across an EEN-WWS striking fault, show sinistral strike-slip along the fault and subsidence of the southern block. Much of the subsidence occurred around the time of the distal M W = 5.6 Pernik Earthquake. An important transient deformation event, which began in autumn 2012, was reflected by significant compression and following extension, across the monitored fault. The data from Bacho Kiro, recorded across a NE-SW striking fault, show sinistral strike-slip along the fault and subsidence of the north-western block. The same important deformation event was reflected by changes in the strike-slip, dip-slip, and horizontal opening/closing trends. These results have been compared to data from other monitoring points in the Western Carpathians, External Dinarides, and Tian Shan. Many of the sites show evidence of simultaneous displacement anomalies and this observation is interpreted as a reflection of the plate-wide propagation of a tectonic pressure pulse towards the end of 2012.
“…This contrasts markedly the generally accepted picture of N-S extension in this part of the Eurasian Plate (e.g. Kotzev et al 2008;Olaiz et al 2009). It suggests that extension can be interrupted periodically by short-lived episodes of crustal stress inversion.…”
Abstract:The EU-TecNet monitoring network uses customized three-dimensional extensometers to record transient deformations across individual faults. This paper presents the first results from two newly established monitoring points in the Balkan Mountains in Bulgaria. The data from Saeva Dupka, recorded across an EEN-WWS striking fault, show sinistral strike-slip along the fault and subsidence of the southern block. Much of the subsidence occurred around the time of the distal M W = 5.6 Pernik Earthquake. An important transient deformation event, which began in autumn 2012, was reflected by significant compression and following extension, across the monitored fault. The data from Bacho Kiro, recorded across a NE-SW striking fault, show sinistral strike-slip along the fault and subsidence of the north-western block. The same important deformation event was reflected by changes in the strike-slip, dip-slip, and horizontal opening/closing trends. These results have been compared to data from other monitoring points in the Western Carpathians, External Dinarides, and Tian Shan. Many of the sites show evidence of simultaneous displacement anomalies and this observation is interpreted as a reflection of the plate-wide propagation of a tectonic pressure pulse towards the end of 2012.
“…Nevertheless, a lithosphere with a dry mantle under shear or tensile regime would be stronger and consistent with the jelly sandwich model. Despite the complex stresses in Iberia, this result also agrees with the tectonic active regimes that mainly characterised its interior (Jiménez-Munt and Negredo, 2003;De Vicente et al, 2008;Olaiz et al-2009); consequently, strike-slip regime (α in [3]) is the upper limit to estimate the brittle strength in this region.…”
Section: The Iberian Intraplate Rheological Model: Strong Vs Soft Masupporting
confidence: 75%
“…Following the criteria proposed in CSN (2006), data prior to 1985 were ruled out (low quality of the network) as well as those with magnitudes less than ficial areas could experience brittle deformation under tensile or shear regime. Therefore, although the intraplate Cenozoic deformations occurred in a compressive context, the shear to extensional conditions best describe the active tectonic regime, as also suggest the inversion of focal mechanisms Olaiz et al, 2009) and the sedimentation of late Miocene alluvial fans (De Vicente and Muñoz-Martín, 2012). Earthquake nucleation are not resolved with these models but the elastic deformation, roughly coincident with the competent layers, and the aseismic creep in the crust and mantle explain the low seismicity of the peninsular centre.…”
Section: Seismicitymentioning
confidence: 93%
“…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). These two zones are linked by a complex region, where the Central System and the basins are located, under strike-slip to uniaxial extensional stress regime and where the intermediate and maximum principal stresses permute from the NW-SE horizontal axis to the vertical.…”
Section: The Central System and The Duero And Madrid Basinsmentioning
Previous studies about the strength of the lithosphere in the center of Iberia fail to resolve the depth of earthquakes because of the rheological uncertainties. Therefore, new contributions are considered (the crustal structure from a density model) and several parameters (tectonic regime, mantle rheology, strain rate) are checked in this paper to properly examine the role of lithospheric strength in the intraplate seismicity and the Cenozoic evolution. The strength distribution with depth, the integrated strength, the effective elastic thickness and the seismogenic thickness have been calculated by a finite element modelling of the lithosphere across the Central System mountain range and the bordering Duero and Madrid sedimentary basins. Only a dry mantle under strike-slip/extension and a strain rate of 10 -15 s , causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. This heterogeneity has been maintained since the Cenozoic and determine the mountain uplift and the biharmonic folding of the Iberian lithosphere during the Alpine deformations. The seismogenic thickness bounds the seismic activity in the upper-middle crust, and the decreasing crustal strength from the Duero Basin towards the Madrid Basin is related to a parallel increase in Plio-Quaternary deformations and seismicity. However, elasto-plastic modelling shows that current African-Eurasian convergence is resolved elastically or ductilely, which accounts for the low seismicity recorded in this region.Keywords: lithospheric strength, effective elastic thickness, seismogenic thickness, Iberia, finite element modelling
ResumenLos estudios previos sobre resistencia de la litosfera en el centro de Iberia no logran resolver la profundidad de los terremotos debido a las incertidumbres reológicas. Por eso, en este trabajo se han considerado nuevas contribuciones (estructura cortical obtenida de un modelo de densidad) y se han comprobado varios parámetros (régimen tectónico, reología del manto, tasa de deformación) para examinar adecuadamente el papel de la resistencia de la litosfera en la sismicidad intraplaca y en la evolución Cenozoica. Mediante una modelización de elementos finitos, se ha calculado la distribución de la resistencia con la profundidad, la resistencia integrada, el espesor elástico efectivo y el espesor sismogénico en una sección litosférica que atraviesa la cadena montañosa del Sistema Central y las cuencas sedimentarias del Duero y Madrid. Sólo un manto seco en desgarre/extensión y una tasa de deformación de 10 -15 s -1, o bajo extensión y 10 -16 s -1 , origina una litosfera resistente. La resistencia integrada y el espesor elástico son más bajos en el sistema montañoso que en las cuencas. Estas anisotropías se han mantenido desde el Cenozoico y determinan el levantamiento de la cadena y el plegamiento biarmónico de la litosfera Ibérica durante las deformaciones alpinas. El espesor sismogénico limita la actividad sísmica en la corteza superior-media, y l...
“…3C). This new stress field is superimposed on the structures generated up to the Lower Miocene and does not have its origin in the northern Edge (Pyrenees), where mainly normal type focal mechanisms are registered (Olaiz et al, 2009). A new Africa-Europe plate boundary was created to the south of the Iberian Peninsula and its formation is still ongoing (De Vicente and Vegas, 2009).…”
Section: Tectonic Setting and Present-day Stress Fieldmentioning
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