Interpretation of controlled source radiomagnetotelluric data in the frequency range 1 kHz - 1 MHz using multidimensional conductivity models

可控源无线大地电磁法（CSRMT）是一种新的和创新的电磁法，用于浅层地下调查，深度约为100米，取决于地下电阻率。 在这个项目中，张量CSRMT测量将首次在1 kHz至1 MHz的扩展频率范围内使用延长的电偶极子源实现。将在俄罗斯两个选定的试验区进行两次调查。使用这种扩展的频率范围和偶极子源的CSRMT远场数据也将首次通过三维反演进行解释。基频在0.1 kHz和150 kHz之间的矩形信号将通过两个约700 m长的相互垂直的接地电偶极子注入。将观察在空间分布的接收器位置处的发射器的远场和近场中的电场和磁场的时间序列。将使用双变量时间序列分析推导出全阻抗和倾翻器传递函数。空间分布的远场CSRMT数据将通过二维和三维反演计算来解释。传统的RMT测量将在发射机不活动期间进行，以增加数据覆盖范围。导出的远场电导率3D CSRMT模型和从RMT数据导出的模型然后将用于通过使用试错法和3D正演计算来解释近场的传递函数。靠近彼得堡的调查区域是一个垃圾填埋区，将对该区域的含水层污染进行调查，而靠近莫斯科的调查区域是一个古山谷，其中嵌入了局部高阻砂岩透镜体。这些古山谷与矿产资源的沉积有关。这些勘测区域的先前地球物理测量和建模（DC、RMT和地震）将用作多维CSRMT建模的约束条件。这两个目标都在大约15米的深度，可以理想地通过CSRMT方法进行探测。

Controlled Source Radiomagnetotellurics (CSRMT) is a new and innovative electromagnetic method for shallow subsurface investigations down to roughly 100 m depth depending on the subsurface resistivity. In this project, tensor CSRMT measurements will be realized for the first time in the extended frequency range from 1 kHz to 1 MHz using a prolonged electric dipole source. Two survey will be conducted on two selected test areas in Russia. CSRMT far field data using such an extended frequency range and dipole source will also be interpreted for the first time by a 3D inversion. A rectangular signal with base frequencies between 0.1 kHz and 150 kHz will be injected through two approximately 700 m long grounded electric dipoles located perpendicular to each other. Time series of the electric and magnetic fields in the far and near field of the transmitter at spatially distributed receiver-locations will be observed. Full impedance and tipper transfer functions will be derived using a bivariate time series analysis. The spatially distributed far field CSRMT data will be interpreted by 2D and 3D inversion calculations. Conventional RMT measurements will be carried out during the time the transmitter is not active to increase data coverage. The derived conductivity 3D CSRMT model of the far field and the model derived from the RMT data will then be used to interpret the transfer functions of the near field by using the trial and error approach and 3D forward calculations. The investigated area close to St. Petersburg is a landfill area where the aquifer contamination will be investigated, whereas the survey area close to Moscow is a paleo-valley in which local high resistive sand lenses are embedded. These paleo-valleys are associated with deposits of mineral resources. Previous geophysical measurements and modellings (DC, RMT & Seismic) on these survey areas will be used as constraints in the multidimensional CSRMT modeling. Both targets are in a depth of about 15m and can be ideally detected by the CSRMT method.