Finite element modelling of inter-seismic deformation associated with Arabia-Eurasia plate convergence in western Lurestan (Iran)

The Zagros thrust belt formed due to the convergence between the Arabian and Eurasian plates during the closure of the Neo-Tethys Ocean. The orogenic process involved three domains: the Arabian passive margin to the SW, the southwestern margin of the Eurasian plate to the NE, and the Central Iranian microplates (Iran block) located in between. GPS measurements show that the northward relative motion of the Arabian Plate is still active today, with oblique convergence occurring at a rate of ca. 2 cm/yr with respect to fixed Eurasia. This active drift produces high-magnitude earthquakes along the Zagros thrust belt, such as the Iran-Iraq border seismic event of November 12, 2017 (M_w = 7.3), nucleated along the "Mountain Front Fault". The aim of this work is to study the inter-seismic deformation that eventually leads to the nucleation of important seismic events in the study area. A 2-D finite element model has been performed starting from published geological sections and relevant seismological datasets, integrated with geo-mechanical parameters of the rocks. Using the Marc software (MSC Software Corporation), model parameters including gravity load, boundary conditions and fault planes friction have been set up in order to obtain the best simulation of the inter-seismic behaviour of the Mountain Front Fault, which was responsible for the seismic event of November 2017. This type of modelling allows one constraining a given fault as being locked or alternatively free to move (in order to simulate stable sliding). Results from several tests allowed us to shed new light onto the inter-seismic deformation loading the seismogenic structure of the November 12, 2017 (M_w = 7.3) earthquake. The results of finite element modelling, including predicted uplift pattern and rate along the analysed crustal section, are compared with a tectonic geomorphology analysis in order to unravel the most reliable tectonic scenario for the active tectonic setting of the study area.