TY - GEN

T1 - On the application of the controlled source radiomagnetotellurics (CSRMT) for near surface exploration

AU - Tezkan, B.

AU - Muttaqien, I.

AU - Saraev, A.

PY - 2018

Y1 - 2018

N2 - Conventional radiomagnetotelluric method (RMT) does not need an active transmitter due to the use of the EM-field of the existing radio transmitters near the survey area. Therefore, it is logistically simple and enablesspatial measurements on the survey area in a short time. However, the method has a big disadvantage: there exist no radio transmitters below 10 kHz. Therefore, the penetration depth is limited. In addition, there may be no sufficient transmitter if a RMT survey will be conducted in a remote area. An alternative solution is to build a transmitter to create the electromagnetic field instead of using the field of existing radio transmitters in the vicinity of the survey area (CSRMT method).A rectangular signal with base frequencies between 0.1 kHz and 150 kHz is injected through a grounded electric dipole. Electric and magnetic field components are observed at these frequencies and at their subharmonics, so that apparent resistivities and phases are observed in a broad frequency range between 1 kHz and 1000 kHz. Inline or broadside configuration can be used. A scalar CSRMT survey was carried out on the buried faults north of St. Petersburg to test the applicability of this method to the mapping of near-surface faults. A 700 m electric dipole with base frequencies of 0.5, 11.3, 30 and 105 kHz was used as a transmitter. Smooth apparent resistivity and phase values as a function of frequency from 1 kHz to 1 MHz were observed in the far field zone for the inline configuration at 57 stations by using a station distance of 20 m. The observed apparent resistivity and phase TM-mode data were interpreted using the 2D inversion algorithm, and a good data fitting could be obtained. The resistivity structure beneath the survey area (down to a depth of 80 m) could be derived and the buried faults could be mapped successfully. An excellent correlation of observed RMT and CSRMT transfer functions and 2D conductivity models was achieved

AB - Conventional radiomagnetotelluric method (RMT) does not need an active transmitter due to the use of the EM-field of the existing radio transmitters near the survey area. Therefore, it is logistically simple and enablesspatial measurements on the survey area in a short time. However, the method has a big disadvantage: there exist no radio transmitters below 10 kHz. Therefore, the penetration depth is limited. In addition, there may be no sufficient transmitter if a RMT survey will be conducted in a remote area. An alternative solution is to build a transmitter to create the electromagnetic field instead of using the field of existing radio transmitters in the vicinity of the survey area (CSRMT method).A rectangular signal with base frequencies between 0.1 kHz and 150 kHz is injected through a grounded electric dipole. Electric and magnetic field components are observed at these frequencies and at their subharmonics, so that apparent resistivities and phases are observed in a broad frequency range between 1 kHz and 1000 kHz. Inline or broadside configuration can be used. A scalar CSRMT survey was carried out on the buried faults north of St. Petersburg to test the applicability of this method to the mapping of near-surface faults. A 700 m electric dipole with base frequencies of 0.5, 11.3, 30 and 105 kHz was used as a transmitter. Smooth apparent resistivity and phase values as a function of frequency from 1 kHz to 1 MHz were observed in the far field zone for the inline configuration at 57 stations by using a station distance of 20 m. The observed apparent resistivity and phase TM-mode data were interpreted using the 2D inversion algorithm, and a good data fitting could be obtained. The resistivity structure beneath the survey area (down to a depth of 80 m) could be derived and the buried faults could be mapped successfully. An excellent correlation of observed RMT and CSRMT transfer functions and 2D conductivity models was achieved

M3 - Conference contribution

BT - Abstracts. 24th EM Induction Workshop, Helsingør, Denmark, August 12-19, 2018

ER -