Abstract
Abstract. The Alpine orogen formed as a result of the collision between the Adriatic and European plates. Significant crustal heterogeneity exists within the region due to the long history of interplay between these plates, other continental and oceanic blocks in the region, and inherited crustal features from earlier orogenies. Deformation relating to the collision continues to the present day. Here, a seismically constrained, 3-D structural and density model of the lithosphere of the Alps and their respective forelands, derived from integrating numerous geoscientific datasets, was adjusted to match the observed gravity field. It is shown that the distribution of seismicity and deformation within the region correlates well to thickness and density changes within the crust, and that the present-day Adriatic crust is both thinner and denser (22.5 km, 2800 kg m−3) than the European crust (27.5 km, 2750 kg m−3). Alpine crust derived from each respective plate is found to show the same trend, with zones of Adriatic provenance (Austro-Alpine unit and Southern Alps) found to be denser and those of European provenance (Helvetic zone and Tauern Window) to be less dense. This suggests that the respective plates and related terranes had similar crustal properties to the present-day ones prior to orogenesis. The model generated here is available for open-access use to further discussions about the crust in the region.
Highlights
The Alps are one of the best-studied mountain ranges in the world, yet significant unknowns remain regarding their crustal structure and links that may exist between the localisation of deformation and seismicity in the region and crustal heterogeneity
Significant amounts of seismicity and deformation correspond to plate dynamics, such as at the convergence of the European and Adriatic plates in north-east Italy (Restivo et al, 2016) where the Adriatic plate is observed to act as a rigid indenter, moving northwards and rotating anticlockwise against the weaker European plate (Nocquet and Calais, 2004; Vrabec and Fodor, 2006; Serpelloni et al, 2016)
Crustal heterogeneities in the European plate, constituting the northern foreland of the Alps, principally derive from different terranes that collided during the Carboniferous age Variscan orogeny (Franke, 2000)
Summary
The Alps are one of the best-studied mountain ranges in the world, yet significant unknowns remain regarding their crustal structure and links that may exist between the localisation of deformation and seismicity in the region and crustal heterogeneity. Numerous large historic seismic events (Fäh et al, 2011; Stucchi et al, 2012; Grünthal et al, 2013), such as the magnitude 6.6 Basel earthquake in 1356 CE, lie substantially intra-plate in areas with low amounts of horizontal surface strain (Sánchez et al, 2018) suggesting that possible inherited features within the crust are significant factors to their localisation. Crustal heterogeneities in the European plate, constituting the northern foreland of the Alps, principally derive from different terranes that collided during the Carboniferous age Variscan orogeny (Franke, 2000).
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