We aim to quantify the likely ranges of magnitudes and directions of forces that may explain present-day natural stresses within the Eurasian plate. We first focus on one of the driving forces, horizontal gravitational stresses (HGSs) resulting from lateral variations in gravitational potential energy, which are particularly relevant in the context of the Eurasian plate because there are no major slabs attached to it (i.e., no slab pull force). We show that different published models of lithospheric density including lateral variations in the lithosphere-asthenosphere boundary result in significantly different HGSs. Other driving forces are mantle convective tractions including dynamic topography, and plate interaction tractions with bounding plates. Second, we include observed major faults into a 2D spherical cap elastic model of the Eurasian plate. We show results of forward FEM calculations based on the best model parameters of Warners et al. (2013) and compare them with observed stress directions. We propose different objective functions that quantify the (relative contributions to the) misfit of the modelled and observed stresses, fault slip directions, and magnitudes, the deviation of the net torque on the plate from zero, and the model representation error. Our study represents a stepping stone towards a Bayesian inference workflow to constrain the dynamics of the Eurasian plate of which we show preliminary results.Warners-Ruckstuhl, K. N., R. Govers, and R. Wortel, 2013, Tethyan collision forces and the stress field of the Eurasian Plate: Geophys. J. Int., v. 195, no. 1, p. 1–15, doi:10.1093/gji/ggt219.
12 Ma ago and since then translated with the Pacific (PAC) plate. The microplates’ transport mechanism has been explained by partial coupling with the PAC plate. According to this theory, the young oceanic lithosphere from the Farallon-Pacific spreading center approaching North America was too buoyant to be subducted. Therefore a zone of increased lithospheric coupling developed between the partially subducted Farallon slabs and the overlying NAM margin. In consequence both, the subduction and the seafloor spreading slowed down and ceased. With the development of this coupling region west of BAJA the main PAC-NAM plate boundary jumped inland east of BAJA, first delocalized in the Protogulf extensional province, and later localized along the Gulf of California. We use a numerical modeling technique to test the dynamic conditions of BAJA transport as seen from present-day and from geologic plate motion studies. Using the kinematic data we test the necessary coupling forces for BAJA transport, as well as, geometrical constraints along the PAC-BAJA coupling zone. Evaluating the transport conditions at different stages of the plate boundary evolution, we want to learn about necessary pre-conditions for the BAJA transfer.
We present a method to estimate the poorly understood mechanical coupling between lithosphere and underlying mantle, and apply it to the Eurasian plate. Mechanical equilibrium of tectonic plates requires the torque from mantle tractions ( M ) to be balanced by the torques from edge forces ( E ) and lithospheric body forces ( B ). The direction of E proves tightly constrained by plate boundary nature but B is affected uncertainties in the density structure of continents. We consistently find that the non‐zero torque required from mantle tractions does not agree with the orientation of any published absolute motion model. We conclude that mechanical balance of the Eurasian plate requires an actively convecting mantle, which should result in a torque on the Eurasian plate located in the southwest Pacific.
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