Thermal Structure and Active Tectonics of the Frontal Zone of the Zagros Fold and Thrust Belt in Western Lurestan, Iran: New Insights from 3-D Geothermal Analytical Modelling and 2-D Structural Finite Element Modelling

In the last century several authors tried to understand the geological and geophysical setting of the Zagros mountain chain. The result of these studies pointed out a mesozoic continental-continental collision between Eurasia and Arabia plates due to the closure of the Neo-Tethys ocean. At the present, the orogenic process is still active. The working area of this thesis is localized in the northern part of the Zagros orogen. In this sector of the Zagros orogen a master blind fault known as Mountain Front Fault and named here Main Frontal Thrust nucleated a large earthquake (Mw = 7.3) in November 12, 2017 highlighting the deep structure of this sector of the Zagros Mountain chain. The aim of this thesis is to explain how the Main Frontal Thrust interacts with the entire Lurestan arc in terms of thermal structure and active deformation. To reach the prefixed scope we used a mathematical approach studying the major thrust fault by analytical and numerical procedures in order to realize exhaustive 2-D and 3-D models. We present here the 3-D model of the Lurestan arc thermal structure calculated using an analytical procedure interpolated with polynomial equations. The model took into account topography, sedimentary cover, basement, thrusts and Moho depth constrained by the physical properties of the rocks as thermal conductivity and heat production rate. To study the active deformation, instead, we realized a 2-D model of co-seismic and inter-seismic deformation of the Main Frontal Thrust applying the finite element modelling methodology performed here using Marc Software (MSC Software Corporation). Both 3-D thermal structure model and 2-D active deformation FEM model were calculated on a geological model describing the main Lurestan arc crustal structures. The geometry of the tectonic features was built on the base of previous published geological cross section. At the end, we compared the obtained thermal structure with previous studies and the active deformation model with an investigation of a large-scale features of topography. The resulted information provided by this thesis is of pivotal importance for any quantitative modelling of the tectonic behaviour of this actively deforming Iran sector, geodynamic studies, as well as in geothermal/hydrocarbon exploration. It may also have important implications for active tectonic studies and seismotectonic modelling in an area recently affected by a Mw > 7 earthquake.