Probabilistic Assessment of the Causes of Active Deformation in Greece, Western Anatolia, and the Balkans Using Finite Element Models

Abstract

We constrain the contribution of driving and resistive regional forces to the observed surface deformation in the Nubia-Eurasia plate boundary region. We use a viscoelastic mechanical model with fault zones representing regional active faults. Deformation is driven by velocities of surrounding plates and by lateral variations in gravitational potential energy. We sample model parameter values in the context of Global Navigation Satellite System observations, based on Bayesian inference. The magnitudes of driving and resistive forces, and viscosity of the overriding plate are search parameters. Velocities of our median model fit the observations very well. Predicted slip directions agree with focal mechanisms on most model fault zones. Slip rakes and rates agree partly with results from previous block modeling studies. We find that significant trench suction forces are required on all trenches. The absence or presence of a net pull along the Nubia slab does not affect the model predictions. Shear tractions from asthenospheric flow have a small imprint on the deformation of the overriding plate. The average viscosity of the Eurasian lithosphere is (Formula presented.) Pa⋅s. Resistive shear traction rates are small along all plate boundary segments, except the Kephalonia fault zone. Resistive shear traction rates are significant along all intraplate fault zones, except the northern branch of the North Anatolian Fault zone. We propose a mechanically consistent method to estimate the rate at which fault zones accumulate slip deficit. We find that average slip deficit rates on model faults range between 0 and 4.5 mm/yr.