scholarly journals tTEM20AAR: a benchmark geophysical dataset for unconsolidated fluvio-glacial sediments

2021 ◽  
Author(s):  
Alexis Neven ◽  
Pradip Kumar Maurya ◽  
Anders Vest Christiansen ◽  
Philippe Renard
Keyword(s):  
Time Domain ◽  
Reliable Method ◽  
Geophysical Inversion ◽  
Quaternary Deposits ◽  
Glacial Sediments ◽  
Time Domain Electromagnetic ◽  
Inversion Techniques ◽  
Alpine Environments ◽  
The Magnetic Field ◽  
Depth Of Investigation

Abstract. Quaternary deposits are complex and heterogeneous. They contain some of the most abundant and extensively used aquifers. In order to improve the knowledge of the spatial heterogeneity of such deposits, we acquired a large (more than 1400 hectares) and dense (20 m spacing) Time Domain ElectroMagnetic (TDEM) dataset in the upper Aare Valley, Switzerland. TDEM is a fast and reliable method to measure the magnetic field directly related to the resistivity of the underground. In this paper, we present the inverted resistivity models derived from this acquisition, and all the necessary data in order to perform different inversions on the processed data (https://doi.org/10.5281/ZENODO.4269887 (Neven et al., 2020)). The depth of investigation ranges between 40 to 120 m depth, with an average data residual contained in the standard deviation of the data. These data can be used for many different purposes: from sedimentological interpretation of quaternary environments in alpine environments, geological and hydrogeological modeling, to benchmarking geophysical inversion techniques.

scholarly journals tTEM20AAR: a benchmark geophysical data set for unconsolidated fluvioglacial sediments

2021 ◽  
Vol 13 (6) ◽  
pp. 2743-2752
Author(s):  
Alexis Neven ◽  
Pradip Kumar Maurya ◽  
Anders Vest Christiansen ◽  
Philippe Renard
Keyword(s):  
Time Domain ◽  
Reliable Method ◽  
Geophysical Inversion ◽  
Quaternary Deposits ◽  
Data Set ◽  
Time Domain Electromagnetic ◽  
Inversion Techniques ◽  
Alpine Environments ◽  
The Magnetic Field ◽  
Depth Of Investigation

Abstract. Quaternary deposits are complex and heterogeneous. They contain some of the most abundant and extensively used aquifers. In order to improve the knowledge of the spatial heterogeneity of such deposits, we acquired a large (1500 ha) and dense (20 m spacing) time domain electromagnetic (TDEM) data set in the upper Aare Valley, Switzerland (available at https://doi.org/10.5281/zenodo.4269887; Neven et al., 2020). TDEM is a fast and reliable method to measure the magnetic field directly related to the resistivity of the underground. In this paper, we present the inverted resistivity models derived from this acquisition. The depth of investigation ranges between 40 and 120 m, with an average data residual contained in the standard deviation of the data. These data can be used for many different purposes: from sedimentological interpretation of quaternary environments in alpine environments, geological and hydrogeological modeling, to benchmarking geophysical inversion techniques.

Modeling induced polarization effects in helicopter time-domain electromagnetic data: Field case studies

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. B49-B61 ◽  
Author(s):  
Vladislav Kaminski ◽  
Andrea Viezzoli
Keyword(s):  
Time Domain ◽  
Signal To Noise Ratio ◽  
Mineral Exploration ◽  
Induced Polarization ◽  
Electromagnetic Transients ◽  
Additional Information ◽  
Time Domain Electromagnetic ◽  
Airborne Electromagnetic ◽  
Cole Model ◽  
Inversion Techniques

Induced polarization (IP) effects are becoming more evident in time-domain helicopter airborne electromagnetic (AEM) data thanks to advances in instrumentation, mainly due to improvements in the signal-to-noise ratio and hence better data quality. Although the IP effects are often manifested as negative receiver voltage values, which are easy to detect, in some cases, IP effects can distort recovered transients in other ways so they may be less obvious and require careful data analysis and processing. These effects represent a challenge for modeling and inversion of the AEM data. For proper modeling of electromagnetic transients, the chargeability of the subsurface and other parameters describing the dispersion also need to be taken into consideration. We use the Cole-Cole model to characterize the dispersion and for modeling of the IP effects in field AEM data, collected by different airborne systems over different geologies and exploration targets, including examples from diamond, gold, and base metal exploration. We determined how multiparametric inversion techniques can simultaneously recover all four Cole-Cole parameters, including resistivity [Formula: see text], chargeability [Formula: see text], relaxation time [Formula: see text], and frequency parameter [Formula: see text]. The results obtained are in good agreement with the ancillary information available. Interpretation of the IP effects in AEM data is therefore seen by the authors as providing corrected electrical resistivity distributions, as well as additional information that could assist in mineral exploration.

Megasource time‐domain electromagnetic sounding methods

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 993-1009 ◽  
Author(s):  
George V. Keller ◽  
James I. Pritchard ◽  
Jimmy Joe Jacobson ◽  
Norman Harthill
Keyword(s):  
Time Domain ◽  
Vertical Component ◽  
High Amplitude ◽  
Colorado School ◽  
Electromagnetic Sounding ◽  
The Earth ◽  
Field Versus ◽  
Time Domain Electromagnetic ◽  
Em Field ◽  
Depth Of Investigation

The Colorado School of Mines time‐domain electromagnetic (EM) sounding system makes use of a grounded length of cable powered with high‐amplitude current square waves to generate an EM field for probing the earth. The vertical component of magnetic induction is detected at a sounding site located at a relatively large distance compared to the desired depth of investigation. With a source moment of a million ampere meters or greater, offset distances of several tens of kilometers can be achieved easily, providing depths of investigation of up to 10 km. The recorded induction field versus time curves are routinely interpreted by comparison with computer‐generated theoretical curves for a layered earth. Megasource EM surveys have been carried out at The Geysers in northern California and near Yakima in central Washington, providing apparently meaningful information on the electrical structure in these areas at depths as great as 10 km.

scholarly journals Lightweight Unmanned Aerial System for Time-Domain Electromagnetic Prospecting—The Next Stage in Applied UAV-Geophysics

2021 ◽  
Vol 11 (5) ◽  
pp. 2060 ◽  
Author(s):  
Alexander Parshin ◽  
Ayur Bashkeev ◽  
Yuriy Davidenko ◽  
Marina Persova ◽  
Sergey Iakovlev ◽  
...  
Keyword(s):  
Time Domain ◽  
Gamma Ray ◽  
Pulse Generator ◽  
Measuring System ◽  
Electromagnetic Sounding ◽  
Mountainous Regions ◽  
Time Domain Electromagnetic ◽  
Unmanned System ◽  
Classical Triad ◽  
The Time Domain

Nowadays in solving geological problems, the technologies of UAV-geophysics, primarily magnetic and gamma surveys, are being increasingly used. However, for the formation of the classical triad of airborne geophysics methods in the UAV version, there was not enough technology for UAV-electromagnetic sounding, which would allow studying the geological environment at depths of tens and hundreds of meters with high detail. This article describes apparently the first technology of UAV-electromagnetic sounding in the time domain (TDEM, TEM), implemented as an unmanned system based on a light multi-rotor UAV. A measuring system with an inductive sensor—an analogue of a 20 × 20 or 50 × 50 m receiving loop is towed by a UAV, and a galvanically grounded power transmitter is on the ground and connected to a pulse generator. The survey is carried out along a network of parallel lines at low altitude with a terrain draping at a speed of 7–8 m/s, the maximum distance of the UAV’s departure from the transmitter line can reach several kilometers, thus the created technology is optimal for performing detailed areal electromagnetic soundings in areas of several square kilometers. The results of the use of the unmanned system (UAS) in real conditions of the mountainous regions of Eastern Siberia are presented. Based on the obtained data, the sensitivity of the system was simulated and it was shown that the developed technology allows one to collect informative data and create geophysical sections and maps of electrical resistivity in various geological situations. According to the authors, the emergence of UAV-TEM systems in the near future will significantly affect the practice of geophysical work, as it was earlier with UAV-magnetic prospecting and gamma-ray survey.

Quasi-2D inversion of DCR and TDEM data for shallow investigations

Geophysics ◽  
2011 ◽  
Vol 76 (4) ◽  
pp. F239-F250 ◽  
Author(s):  
Fernando A. Monteiro Santos ◽  
Hesham M. El-Kaliouby
Keyword(s):  
Joint Inversion ◽  
Synthetic Data ◽  
Data Sets ◽  
Complex Environments ◽  
Inversion Algorithm ◽  
2D Inversion ◽  
New Approach ◽  
Earth Models ◽  
Time Domain Electromagnetic ◽  
Inversion Techniques

Joint or sequential inversion of direct current resistivity (DCR) and time-domain electromagnetic (TDEM) data commonly are performed for individual soundings assuming layered earth models. DCR and TDEM have different and complementary sensitivity to resistive and conductive structures, making them suitable methods for the application of joint inversion techniques. This potential joint inversion of DCR and TDEM methods has been used by several authors to reduce the ambiguities of the models calculated from each method separately. A new approach for joint inversion of these data sets, based on a laterally constrained algorithm, was found. The method was developed for the interpretation of soundings collected along a line over a 1D or 2D geology. The inversion algorithm was tested on two synthetic data sets, as well as on field data from Saudi Arabia. The results show that the algorithm is efficient and stable in producing quasi-2D models from DCR and TDEM data acquired in relatively complex environments.

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