UXO detection and prioritization using combined airborne vertical magnetic gradient and time‐domain electromagnetic methods

2008 ◽  
Author(s):  
Jacob Sheehan ◽  
Les Beard ◽  
Jeffrey Gamey ◽  
William Doll ◽  
Jeannemarie Norton
Keyword(s):  
Time Domain ◽  
Magnetic Gradient ◽  
Electromagnetic Methods ◽  
Time Domain Electromagnetic

Applicability of frequency-domain and time-domain electromagnetic methods for mountain permafrost studies

2001 ◽  
Vol 12 (1) ◽  
pp. 39-52 ◽  
Author(s):  
Christian Hauck ◽  
Mauro Guglielmin ◽  
Ketil Isaksen ◽  
Daniel Vonder Mühll
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Electromagnetic Methods ◽  
Mountain Permafrost ◽  
Time Domain Electromagnetic

Electromagnetic mapping of saline contamination at an active brine pit

1996 ◽  
Vol 33 (2) ◽  
pp. 309-323 ◽  
Author(s):  
I J Ferguson ◽  
W J Taylor ◽  
K Schmigel
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Power Lines ◽  
Late Time ◽  
Signal Distortion ◽  
Electromagnetic Methods ◽  
Time Domain Electromagnetic ◽  
Survey Results ◽  
Limited Degree ◽  
Cultural Noise

Frequency-domain and time-domain electromagnetic methods were used to investigate groundwater contamination at an active brine pit in southwestern Manitoba, Canada. The objectives of the survey were to delineate contamination suspected to be occuring at the site and to compare frequency-domain electromagnetic (FDEM) and time-domain electromagnetic (TDEM) measurements in a survey area containing pipelines, fences, and power lines. The survey successfully delineated a region of high conductivity around brine pit, confirming that leakage is occurring from the pit. Modelling of the FDEM results suggests the contamination is spreading within a series of shallow sand units. Comparison of FDEM and TDEM survey results indicate that small-separation FDEM systems are much more useful for mapping in a developed area containing sources of cultural noise. The FDEM systems permit rapid mapping of spatial variations in conductivity, are affected to only a limited degree by cultural features, and provide some resolution of the depth variation of conductivity at shallow depth. It was not possible to obtain useful TDEM measurements anywhere near the active brine pit because of the signal distortion in the late-time response. Key words: geophysics, electromagnetic, brine pit, saline contamination.

A comparison of loop time-domain electromagnetic and short-offset transient electromagnetic methods for mapping water-enriched zones — A case history in Shaanxi, China

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. B201-B208 ◽  
Author(s):  
Weiying Chen ◽  
Guoqiang Xue ◽  
Afolagboye Lekan Olatayo ◽  
Kang Chen ◽  
Muhammad Younis Khan ◽  
...  
Keyword(s):  
Time Domain ◽  
Mining Depth ◽  
Transient Electromagnetic ◽  
Resolution Capability ◽  
Electromagnetic Methods ◽  
Detection Depth ◽  
Reliable Detection ◽  
Time Domain Electromagnetic ◽  
Tem Method ◽  
And Inversion

Increases in the mining depth of coal pose a significant challenge to the conventional loop source time-domain electromagnetic (TEM) method that requires significant enlargement of the loop size and transmitting current to realize the deeper sounding results required. As an alternative, TEM devices based on a grounded wire source are generally used to solve detections deeper than several hundred meters. To map the water-enriched zones buried underneath approximately 1000 m at a coal mine in Shaanxi, China, loop TEM and short-offset transient electromagnetic (SOTEM) measurements were conducted. We carried out 1D forward modeling and inversion constrained by drilling informa-tion, and the results reveal that the resolution capability of loop TEM and SOTEM is almost the same in detecting a conductive layer in the absence of any noise. However, for a given noise level and decay time, the SOTEM method provides a deeper investigation than loop TEM without compromising sensitivity. The field examples validated the synthetic results. The loop TEM with dimensions of [Formula: see text] realized a maximum depth of 1000 m, whereas the reliable detection depth of 1500 m was achieved by using a 723 m long grounded wire source using the SOTEM method. Moreover, the labor required is significantly reduced, and the efficiency is dramatically raised using the SOTEM method. Our results predict that the SOTEM method should play a more important role in deep hydrogeophysical investigations.

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