TY - GEN

T1 - Testing of the controlled source radiomagnetotellurics at the study of a granite-gneiss massif in India

AU - Shlykov, Arseny

AU - Saraev, Alexander

AU - Singh, Akarsh

AU - Sudha, Sudha

AU - Tezkan, Bulent

PY - 2019/11/27

Y1 - 2019/11/27

N2 - The radiomagnetotelluric (RMT) method has been applied successfully to different environmental, engineering and geological targets in the last ten years. It uses military and civilian radio transmitters broadcasting in a frequency range between 10 kHz and 1 MHz as active source. A significant disadvantage of the RMT method is the lack of suitable and stable transmitters if the survey area is located in a remote area. Therefore, the application of the method is often limited in such regions. In addition, there exist no transmitters broadcasting below 10 kHz so that the penetration depth of the method is limited. Therefore, the controlled source radiomagnetotelluric (CSRMT) method is developed last years. Both horizontal magnetic and electric dipoles are used as sources in the CSRMT method.We carried out an experiment by the CSRMT method with a horizontal electric dipole source on a granite-gneiss massif in the Ananda Nagar area (Odisha, India). The aim of experiment was to study the ability of the CSRMT method to map a boundary between Archean crystalline rocks and conductive clayey weathering crust and to separate blocks of the massif with different electric properties. In this experiment we compared far-field and transition zone responses of the high-frequency horizontal electric dipole using 1D and 2D isotropic and anisotropic inversion. For the testing of influence of the transverse anisotropy we compared broadside and inline CSRMT data and electric resistivity tomography results.The results of the inversion of CSRMT data correlate well with the drilling. Comparison of the inversion results for the far-field zone (plane wave) and the transition zone of the source shows that, according to CSRMT, in the transition zone it is possible to estimate the anisotropy coefficient of granite-gneisses, changed as a result of secondary processes. The results of anisotropic inversion in the transition zone make it possible to obtain additional information about the geoelectric properties of the section. The massif of granite-gneisses is divided into different blocks with increasing and decreasing of the anisotropy coefficient, the values of which vary from 1.2 to 2.1.This study was supported by the Russian Foundation for Basic Researches, projects 17-55-45042 and 18-505-12033.

AB - The radiomagnetotelluric (RMT) method has been applied successfully to different environmental, engineering and geological targets in the last ten years. It uses military and civilian radio transmitters broadcasting in a frequency range between 10 kHz and 1 MHz as active source. A significant disadvantage of the RMT method is the lack of suitable and stable transmitters if the survey area is located in a remote area. Therefore, the application of the method is often limited in such regions. In addition, there exist no transmitters broadcasting below 10 kHz so that the penetration depth of the method is limited. Therefore, the controlled source radiomagnetotelluric (CSRMT) method is developed last years. Both horizontal magnetic and electric dipoles are used as sources in the CSRMT method.We carried out an experiment by the CSRMT method with a horizontal electric dipole source on a granite-gneiss massif in the Ananda Nagar area (Odisha, India). The aim of experiment was to study the ability of the CSRMT method to map a boundary between Archean crystalline rocks and conductive clayey weathering crust and to separate blocks of the massif with different electric properties. In this experiment we compared far-field and transition zone responses of the high-frequency horizontal electric dipole using 1D and 2D isotropic and anisotropic inversion. For the testing of influence of the transverse anisotropy we compared broadside and inline CSRMT data and electric resistivity tomography results.The results of the inversion of CSRMT data correlate well with the drilling. Comparison of the inversion results for the far-field zone (plane wave) and the transition zone of the source shows that, according to CSRMT, in the transition zone it is possible to estimate the anisotropy coefficient of granite-gneisses, changed as a result of secondary processes. The results of anisotropic inversion in the transition zone make it possible to obtain additional information about the geoelectric properties of the section. The massif of granite-gneisses is divided into different blocks with increasing and decreasing of the anisotropy coefficient, the values of which vary from 1.2 to 2.1.This study was supported by the Russian Foundation for Basic Researches, projects 17-55-45042 and 18-505-12033.

M3 - Conference contribution

BT - 1st Indian Near Surface Geophysics Conference 28-29 November 2019, New Delhi India

CY - Нью Дели, Индия

ER -