3D instantaneous dynamics modeling of present day Aegean subduction

To study the sensitivity of surface observables to subduction and mantle flow, i.e. the coupling of crustal tectonics and the underlying mantle dynamics, we have developed 3D numerical models of the instantaneous crust-mantle dynamics of the eastern Mediterranean. These models comprise both a realistic crust-lithosphere system and the underlying mantle. For this presentation we focus on the regional crustal flow response to the present-day Aegean subduction system.
The set-up of our curved model domain measuring 40◦x40◦x2900km is based on geological and geophysical data of the eastern Mediterranean. We first create a 3D synthetic geometry of the crust-lithosphere system in a stand- alone program, including the present-day configuration of the plates in the region and crust and lithosphere thickness variations abstracted from Moho and LAB maps. In addition we construct the geometry of the Aegean slab from a seismic tomography model and earthquake hypocenters. Geometries are then imported into the finite element code ASPECT [2,3] using specially designed plugins.
The mantle initial temperature conditions can include deviations from an adiabatic profile obtained from conversion of seismic velocity anomalies to temperature anomalies using a depth-dependent scaling. We model compressible mantle flow for which material properties are obtained from thermodynamics P-T lookup-tables (Perple X [1]) in combination with nonlinear viscoplastic rheology laws. Plate motion is prescribed at the model sides in terms of relative as well as absolute plate motion velocities, while a free-slip surface accommodates internal deformation. In short, the forcing in our models comprises lateral pressure gradients, mantle buoyancy and forcing related to the prescribed plate motions.
Based on the above initial and boundary conditions, we obtain model predictions of the regional flow field. Focusing on the crust, these represent predictions of the GPS velocity field that we can compare to actual GPS data. Our initial models provide a good overall fit to the direction and magnitude of these GPS velocities (see Figure). Subsequent models include constructed variations in subduction morphology, slab segmentation, fault zone geometry and boundary conditions. Changes in the resulting model predictions either improve or lessen our fit to the GPS velocity field and help determine the controls of mantle dynamics on present-day tectonic deformation in the Aegean region. This enables us to characterize the general sensitivity of surface observables to plate motions, mantle flow and slab dynamics and to further quantify the coupling of crust and mantle dynamics.
[1] Connolly, J. A. D. (2009). Geochem. Geophys., 10, Q10014. [2] Heister et al. (2017). Geophys. J. Int., 210, 833851.
[3] Kronbichler et al. (2012). Geophys. J. Int., 191, 1229.