Can TEM methods accurately measure depths of less than 50 meters?

Introduction

Transient Electromagnetic (TEM) methods are widely used in geophysical surveys to determine subsurface resistivity structures. These methods are particularly valued for their ability to achieve significant depths of investigation with relatively simple field setups. However, the accuracy and effectiveness of TEM methods in measuring shallow depths, particularly those less than 50 meters, have been a subject of research and debate.

Key Insights

Limitations in Shallow Depths:
- TEM methods are generally not well-suited for shallow soundings (less than 40-50 meters) due to limitations in current instrumentation and signal-to-noise ratios.
Success in Specific Conditions:
- In certain environments, such as underwater or muddy deposits, TEM methods have successfully mapped structures at depths greater than 50 meters, but these studies often focus on deeper layers and may not provide high resolution for depths less than 50 meters .
Technological Improvements:
- Advances in receiver systems and noise reduction techniques have improved the shallow resolution of TEM methods, but these improvements are often aimed at enhancing deeper investigations rather than specifically targeting shallow depths.
Specialized Applications:
- Some specialized TEM configurations, such as fast-sampling systems and UAV-based surveys, have shown potential for high-resolution imaging of the top 10 to 50 meters, but these applications are still under refinement and may not be universally applicable .

Conclusion

While TEM methods have shown significant advancements and capabilities in geophysical surveys, their accuracy in measuring depths of less than 50 meters remains limited. Current instrumentation and techniques are generally more effective for deeper investigations, although specialized configurations and technological improvements are gradually enhancing shallow depth resolution. Further refinement and targeted development are needed to reliably use TEM methods for shallow subsurface investigations.

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Can TEM methods accurately measure depths of less than 50 meters?

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Evaluation of Transient Electromagnetic Soundings for Deep Detection of Conductive Fluids

Transient electromagnetic sounding methods (TEM) effectively detect deep conductive fluids, such as saltwater interfaces in the Floridan Aquifer, but are not suitable for shallow soundings.

Delineating Lake Bottom Structure by TEM on Water Surface

TEM technique can effectively delineate lake bottom structure, revealing a mud/shale inter-bed with a depth of over 50 meters and potential for further refinement in survey parameters.

Noise reduction in TEM: Presenting a bandwidth- and sensitivity-optimized parallel recording setup and methods for adaptive synchronous detection

A bandwidth- and sensitivity-optimized parallel recording setup and adaptive synchronous detection methods significantly improve the achievable depth of investigation in TEM, while maintaining shallow resolution.

Delineating Lake Bottom Structure by TEM on Water Surface

TEM technique can effectively map under-water lake structures, revealing a mud/shale inter-bed with a depth of over 50 meters and suggesting a lake dipping to the southeast.

Semi-Airborne UAV-TEM System Data Inversion with S-Plane Method—Case Study over Lake Baikal

The new UAV-TEM system significantly improves data quality and can replace conventional ground-based electromagnetic surveys in delineating subsurface electrical stratigraphy at depths up to 300 meters in Lake Baikal.

Fast-sampling EM Applied to the River Murray and Surrounding Floodplains in Australia

Fast-sampling TEM systems can provide high-resolution images of the top 10 to 50 meters of the Earth's surface, providing insights into underlying hydrogeology and allowing for continuous data collection.

Application of TEM in detecting water-rich area in coal mines

TEM effectively detects water-rich areas in coal mines, providing a basis for safe production and ensuring water content increases with depth.

Shallow Marine Test of MTEM Method

The MTEM method effectively detects earth impulse responses in shallow marine waters, with potential applications in detecting Earth's rotation at depths up to 2 km.

Testing the limits of AEM bathymetry with a floating TEM system

The floating TEM system effectively tests the accuracy of the AEM method for measuring water depth and sediment thickness in shallow coastal waters, with long stacking times reducing uncertainty in altitude.

Remote characterisation of shallow seafloor using airborne TEM

Airborne TEM systems can accurately predict water depths and sediment thickness in shallow seas, with potential for seafloor characterisation and mapping.

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