TY - JOUR
T1 - tTEM — A towed transient electromagnetic system for detailed 3D imaging of the top 70 m of the subsurface
AU - Auken, Esben
AU - Foged, Nikolaj
AU - Larsen, Jakob Juul
AU - Lassen, Knud Valdemar Trøllund
AU - Maurya, Pradip Kumar
AU - Møller Dath, Søren
AU - Eiskjær, Tore Tolstrup
PY - 2019/1/1
Y1 - 2019/1/1
N2 - ABSTRACTThere is a growing need for detailed investigation of the top 30-50 m of the subsurface, which is critical for infrastructure, water supply, aquifer storage and recovery, farming, waste deposits, and construction. Existing geophysical methods are capable of imaging this zone; however, they have limited efficiency when it comes to creating full 3D images with high resolution over dozens to hundreds of hectares. We have developed a new and highly efficient towed transient electromagnetic (tTEM) system, which is capable of imaging the subsurface up to depth of 70 m at a high resolution, horizontally and vertically. Towed by an all-terrain vehicle, the system uses a 2×4 m transmitter coil and has a z-component receiver placed at 9 m offset from the transmitter. The tTEM uses dual transmitter moment (low and high moment) measurement sequence to obtain the early and late time gates corresponding to shallow and deep information about the subsurface layers. The first bias-free gate is as early as 4 μs from beginning of the ramp (1.4 μs after end of ramp). Data are processed and inverted using methods directly adopted from airborne electromagnetics. The system has been successfully used in Denmark for various purposes, e.g., mapping raw materials, investigating contaminated sites, and assessing aquifer vulnerability. We have also used the tTEM system in the Central Valley of California (United States) for locating artificial recharge sites and in the Mississippi Delta region, to map complex subsurface geology in great detail for building hydrogeologic models.
AB - ABSTRACTThere is a growing need for detailed investigation of the top 30-50 m of the subsurface, which is critical for infrastructure, water supply, aquifer storage and recovery, farming, waste deposits, and construction. Existing geophysical methods are capable of imaging this zone; however, they have limited efficiency when it comes to creating full 3D images with high resolution over dozens to hundreds of hectares. We have developed a new and highly efficient towed transient electromagnetic (tTEM) system, which is capable of imaging the subsurface up to depth of 70 m at a high resolution, horizontally and vertically. Towed by an all-terrain vehicle, the system uses a 2×4 m transmitter coil and has a z-component receiver placed at 9 m offset from the transmitter. The tTEM uses dual transmitter moment (low and high moment) measurement sequence to obtain the early and late time gates corresponding to shallow and deep information about the subsurface layers. The first bias-free gate is as early as 4 μs from beginning of the ramp (1.4 μs after end of ramp). Data are processed and inverted using methods directly adopted from airborne electromagnetics. The system has been successfully used in Denmark for various purposes, e.g., mapping raw materials, investigating contaminated sites, and assessing aquifer vulnerability. We have also used the tTEM system in the Central Valley of California (United States) for locating artificial recharge sites and in the Mississippi Delta region, to map complex subsurface geology in great detail for building hydrogeologic models.
KW - 3d
KW - Electromagnetics
KW - Imaging
KW - Time domain
UR - http://www.scopus.com/inward/record.url?scp=85057545573&partnerID=8YFLogxK
U2 - 10.1190/geo2018-0355.1
DO - 10.1190/geo2018-0355.1
M3 - Journal article
SN - 0016-8033
VL - 84
SP - E13-E22
JO - Geophysics
JF - Geophysics
IS - 1
ER -