Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

Previous studies about the strength of the lithosphere in the Iberia centre 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-1, or under extension and 10-16 s-1, causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. These anisotropies have 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.

Ecohumanists. Protection of physical ecology demands respect human ecology

What is the human being? Which is its origin and its end? What is the influence of the nature in the man and what is his impact on nature? Forthe animalists, men are like other animals; freedom and rationality are not signs of superiority, nor having rights over the animals. For the ecohumanists, human beings are part of nature, but is qualitatively different and superior to animals; and is the creator of the civilization. We analyze these two ecological looks. A special point is the contribution ofecohumanists -from the first half of the Renaissance, who dealt in extenso the dignity and freedom of the human being-, of Michelangelo and finally, of Mozart, through his four insurmountable operas, which display the difficulty of physical ecology to engender so much beauty, so much wealth, so much love for the creatures and so much variety.