Magnetotelluric investigation of the northern part of the Zagros orogenic belt

北部的扎格罗斯山带是欧洲板块和阿拉伯板块碰撞的年轻碰撞区。这通常会导致破坏性的大地震。目前，两种相互竞争的假说表明，伊朗中部以下的阿拉伯板块存在不同的逆冲过程，有和没有板块剥离。因此，人们对潜在的构造模式及其含义知之甚少。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能够区分这些相互冲突的模型。因此，我们在伊朗西北部扎格罗斯山脉北部进行的大地电磁（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测一直被解释为依赖于突出的地质特征。不过，目前尚不清楚这些发现是否与地幔流动或岩石圈中的应力或两者的结合有更强的关系。地震和MT结果的联合解释将大大提高对扎格罗斯山脉构造和构造演化的认识，特别是将其与之前在南部的MT研究结果进行比较。此外，电性各向异性的论证以及与地震各向异性的比较将为地球物理学界以及测量区域的岩石学和流变学提供有价值的信息。该项目包括三个450公里长的NE-SW剖面，间隔约30公里。两个长周期MT剖面各有5个测点，将提供岩石圈深部电导率结构的信息。具有23个台站的宽带大地电磁学剖面跨越了主要的地质单元，分解了上部岩石圈的地壳结构。根据物流工作和随后的3D分析，优化了站点设置。数据处理使用法兰克福软件包FFMT。电性各向异性的指示是通过评估复视电阻率张量和倾卸矢量的空间分布和频率依赖关系得到的。相位张量（PT）由于无电流畸变而成为数据可视化和解释的重要工具。传递函数用ModEM（一种计算各向同性三维电导率异常的反演代码）建模。模型响应。然后通过法兰克福集团与COMSOL Multiphysics®开发的各向异性3D正演建模代码改进数据拟合。该项目包括首次解释Zagros山脉北部的MT数据。我们的研究结果将有助于描述扎格罗斯碰撞带北部的变形是如何被调节的，并将其与更早的造山运动进行比较，从而为所涉及的板块构造过程提供新的见解。

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.