Modelling tectonic deformation along the North-Anatolian Fault in the Sea of Marmara

Using analogue techniques, we attempted to model the complex tectonic deformation pattern observed along the North-Anatolian Fault in the Sea of Marmara from morpho-bathymetry and seismic reflection images. In particular this paper focuses on the so-called Cinarcik segment of the fault connecting the eastern Izmit segment, which entirely ruptured during the Mw 7.4, 1999 earthquake, to the western segment of the Central High. The Çınarcık segment, potentially loaded after the Izmit earthquake, is expected to rupture during an earthquake occurring in the near future, possibly the next decades, with a high potential to affect the Istanbul metropolitan area. Our analysis suggests that the development of the observed structures accommodating strike-slip, transtensional and transpressional deformations, could be explained by changes in the geometry of fault segments within a right-lateral strike-slip tectonic regime. Tectonic deformations were reproduced in the analogue model by imposing a small (about 10°) and sharp difference in the relative orientations of the strike-slip segments at the edges of a major releasing bend. In the model slower strain accumulation occurs along the analogue of the Çınarcık segment than along the analogue of the Izmit segment of the fault. This would predict a delay for earthquakes triggered by stress transfer between the Izmit and Çınarcık segments. The model further predicts that most of the deformation in the Çınarcık basin is controlled by the sharp changes in the geometry of the fault itself

Shape evolution and finite deformation pattern in analogue experiments of lithosphere necking

Lithosphere necking evolution determines the 3-D architecture of crustal and upper mantle thinning and related basins, and the heat flow distribution in rifted regions. Despite a large number of studies, lithosphere necking evolution is still a matter of debate. We present the result from lithospheric-scale analog models designed for investigating the necking shape during extension and the vertical distribution of finite deformation in the mechanical lithosphere. In our experiments, lithosphere necking is asymmetric and, in particular, the 3-D distribution of thinning is cylindrical in the crust and very heterogeneous in the mantle. Overall, the evolution of rifting and necking progresses from delocalized to localized deformation

Centrifuge modelling of thrust systems in the brittle crust: Role of frictional décollement geometry

Centrifuge analogue modelling has provided significant insights into the evolution and architecture of fold and thrust systems. However, all previous works focused on the deformation of viscous and/or plastic layers, and did not analyze the development of structures in the brittle crust. In this work, we present the results of analogue centrifuge models reproducing compression of purely brittle upper crustal layers. We run enhanced gravity models investigating the role exerted by frictional décollements on the evolution and architecture of thrusting and compared the results with new normal-gravity models with similar set-up. In line with the results of previous experimental works, our models show that the presence of a low-friction basal décollement significantly influences the evolution and pattern of thrust systems. By reducing the basal friction of the experimental wedge or the sector of the wedge where the low-friction décollement is located, this layer promotes experimental wedges with low tapers and low heights in the inner portion. Moreover, when a low-friction basal décollement occurs, the tectonic wedge is characterized by an increase in wavelength of thrust sheets toward the foreland, compared to the purely brittle models. Results show a good comparison between centrifuge and normal gravity models, indicating that the centrifuge technique can be successfully used to model shortening in the brittle crust and therefore to analyze the evolution and architecture of thrust systems