Magnetotelluric investigation of the northern part of the Zagros orogenic belt

北方扎格罗斯山带是欧洲板块和阿拉伯板块碰撞的年轻碰撞带。这通常会导致大规模的破坏性地震。 目前，两个相互竞争的假设宣布不同的俯冲过程中的阿拉伯板块低于伊朗中部的板块剥离和不剥离。因此，基本的构造模型及其含义知之甚少。然而，从这些研究中得出的假设电导率分布的数值模拟表明，MT是能够区分这些相互冲突的模型。因此，我们在伊朗西北部北方扎格罗斯山脉进行的大地电磁（MT）调查将有助于解决目前有争议的问题。伊朗西北部地震各向异性的观察被解释为取决于突出的地质特征。尽管目前尚不清楚这些结果是否与地幔流或岩石圈应力或两者的结合有更强的相关性，但地震和MT结果的联合解释将显著增强对扎格罗斯山脉结构和构造演化的理解，特别是通过与南部地区以前的MT研究进行比较。此外，电各向异性的演示和与地震各向异性的比较将为地球物理界以及测量区域的岩石学和流变学提供有价值的信息。两条长周期MT剖面（各5个测站）将提供岩石圈深部电导率结构的信息。23个测站的宽频带MT剖面穿越了主要地质单元，溶解了岩石圈上部的地壳结构。根据物流工作量和随后的3D分析对测站设置进行了优化。数据使用法兰克福软件包FFMT进行处理。通过计算复视电阻率张量和倾复矢量的空间分布和频率依赖性，获得了电各向异性的指示。相位张量（PT）已成为数据可视化和解释的重要工具，因为它是免费的电流失真。传递函数建模与ModEM，反演代码计算的各向同性三维电导率异常。模型响应然后，通过法兰克福小组使用COMSOL Multiphysics®开发的各向异性3D正演模拟代码改进数据拟合。该项目包括首次解释北方扎格罗斯山脉的MT数据。我们的研究结果将有助于描述变形已被容纳在北方扎格罗斯碰撞带，并将其与旧造山带进行比较，从而提供了新的见解板块构造过程。

The northern Zagros mountain belt is a young collisional zone where the European and Arabian plates collide. This regularly results in large, destructive earthquakes. Currently, two competing hypotheses proclaim different underthrusting processes of the Arabian plate below central Iran with and without slab detachment. Accordingly, the underlying tectonic models and their implications are poorly understood. However, numerical simulations of hypothetical electrical conductivity distributions derived from these studies show that MT is capable of distinguishing between these conflicting models. Our magnetotelluric (MT) investigation in the northern Zagros Mountains in NW Iran would thus contribute to the solution of a currently controversial issue.The observation of seismic anisotropy in NW Iran has been interpreted to depend on prominent geological features. Albeit, it is not clear whether these findings are related more strongly to mantle flow or stress in the lithosphere or a combination of both.The joint interpretation of the seismic and MT results will significantly enhance the understanding of the structure and tectonic evolution of the Zagros Mountains, especially by comparing it with previous MT studies in the southern part. Furthermore, the demonstration of the electrical anisotropy and the comparison with the seismic anisotropy will provide valuable information for the geophysical community as well as for the petrology and rheology in the area of measurement.The project comprises three 450 km long NE-SW profiles, which are about 30 km apart. Two long-periodic MT profiles with 5 stations each will provide information about conductivity structures in the deep lithosphere. The broadband MT profile with 23 stations crosses the main geological units and dissolves crustal structures in the upper lithosphere. The station setup is optimized with regard to the logistic effort and the subsequent 3D analysis.The data are processed using the Frankfurt software package FFMT. Indications of electrical anisotropy are obtained by evaluating the spatial distribution and frequency dependence of the complex apparent resistivity tensors and tipper vectors. The phase tensor (PT) has become an important tool for data visualization and interpretation because it is free of galvanic distortion. The transfer functions are modelled with ModEM, an inversion code for the calculation of isotropic 3D conductivity anomalies. The model resp. data fitting is then improved by an anisotropic 3D forward modelling code developed by the Frankfurt group with COMSOL Multiphysics®. The project includes the first interpretation of MT data in the northern Zagros Mountains. Our results will help to describe how the deformation has been accommodated in the northern Zagros collision zone and to compare it with that in older orogenies, thus providing new insights into the plate tectonic processes involved.