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Esben Auken

Overly steep decays in airborne TEM data and their link to chargeability: example from the Howards East District, NT, Australia

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Overly steep decays in airborne TEM data and their link to chargeability: example from the Howards East District, NT, Australia. / Steklova, Klara; Lawrie, Ken; Auken, Esben et al.
In: Exploration Geophysics, Vol. 2019, No. 1, 2019.

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Steklova K, Lawrie K, Auken E, Christiansen AV, Fiandaca G. Overly steep decays in airborne TEM data and their link to chargeability: example from the Howards East District, NT, Australia. Exploration Geophysics. 2019;2019(1). doi: 10.1080/22020586.2019.12073088

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@article{ac35607e34cb4853b85b7ade56e11b9a,
title = "Overly steep decays in airborne TEM data and their link to chargeability: example from the Howards East District, NT, Australia",
abstract = "The induced polarization (IP) response in airborne electromagnetic data has recently received attention due to its potential significance for mineral exploration and envi-ronmental applications, while also holding the prospect of improved geophysical models. A typical IP response produces negative transients in the late time gates. How-ever, under certain circumstances, the presence of overly steep decays in themselves indicate the presence of chargeable material in the subsurface, i.e. where the chargeability is not strong enough to reverse the sign above the noise level, although it still decreases the sig-nal. In this contribution, we analyse a survey in the Howards East District in Northern Territory, Australia, and synthetic data. After a standard processing and removal of all noisy and negative data, we proceeded with a standard inversion that resulted in poor fit and unrealistic high resistivity in deeper layers in parts of the survey. Next, we inverted the data with a dispersive earth model, i.e. including the IP parameters. In the parts of the survey where the data could be fitted well with the “resistivity only” inversion the models changed minimally. In the remaining part, mostly with overly steep decays, the inverted models show chargeable, relatively shallow layers, the unrealistic high resistivity was not present anymore and in general, the data residuals dropped to be within the uncertainty of the data. We further analysed the data, specifically: 1) the sound-ings linked to chargeable areas; 2) the loss of information due to neglecting the negative or late time data with synthetic models; and 3) we explored the ability of the IP inversion models to recover the moderately chargeable layers. In conclusion, a large-scale airborne IP inversion was executed without any specific processing. Until now a time-consuming specific processing seemed to be a necessary step towards a successful IP inversion with airborne data.",
keywords = "airborne TEM, field data application, induced polarization, large-scale AEMIP inversion",
author = "Klara Steklova and Ken Lawrie and Esben Auken and Christiansen, {Anders V.} and Gianluca Fiandaca",
note = "Publisher Copyright: {\textcopyright} 2019, Taylor and Francis. All rights reserved.",
year = "2019",
doi = "10.1080/22020586.2019.12073088",
language = "English",
volume = "2019",
journal = "Exploration Geophysics",
issn = "0812-3985",
publisher = "C S I R O Publishing",
number = "1",

}

RIS

TY - JOUR

T1 - Overly steep decays in airborne TEM data and their link to chargeability

T2 - example from the Howards East District, NT, Australia

AU - Steklova, Klara

AU - Lawrie, Ken

AU - Auken, Esben

AU - Christiansen, Anders V.

AU - Fiandaca, Gianluca

N1 - Publisher Copyright: © 2019, Taylor and Francis. All rights reserved.

PY - 2019

Y1 - 2019

N2 - The induced polarization (IP) response in airborne electromagnetic data has recently received attention due to its potential significance for mineral exploration and envi-ronmental applications, while also holding the prospect of improved geophysical models. A typical IP response produces negative transients in the late time gates. How-ever, under certain circumstances, the presence of overly steep decays in themselves indicate the presence of chargeable material in the subsurface, i.e. where the chargeability is not strong enough to reverse the sign above the noise level, although it still decreases the sig-nal. In this contribution, we analyse a survey in the Howards East District in Northern Territory, Australia, and synthetic data. After a standard processing and removal of all noisy and negative data, we proceeded with a standard inversion that resulted in poor fit and unrealistic high resistivity in deeper layers in parts of the survey. Next, we inverted the data with a dispersive earth model, i.e. including the IP parameters. In the parts of the survey where the data could be fitted well with the “resistivity only” inversion the models changed minimally. In the remaining part, mostly with overly steep decays, the inverted models show chargeable, relatively shallow layers, the unrealistic high resistivity was not present anymore and in general, the data residuals dropped to be within the uncertainty of the data. We further analysed the data, specifically: 1) the sound-ings linked to chargeable areas; 2) the loss of information due to neglecting the negative or late time data with synthetic models; and 3) we explored the ability of the IP inversion models to recover the moderately chargeable layers. In conclusion, a large-scale airborne IP inversion was executed without any specific processing. Until now a time-consuming specific processing seemed to be a necessary step towards a successful IP inversion with airborne data.

AB - The induced polarization (IP) response in airborne electromagnetic data has recently received attention due to its potential significance for mineral exploration and envi-ronmental applications, while also holding the prospect of improved geophysical models. A typical IP response produces negative transients in the late time gates. How-ever, under certain circumstances, the presence of overly steep decays in themselves indicate the presence of chargeable material in the subsurface, i.e. where the chargeability is not strong enough to reverse the sign above the noise level, although it still decreases the sig-nal. In this contribution, we analyse a survey in the Howards East District in Northern Territory, Australia, and synthetic data. After a standard processing and removal of all noisy and negative data, we proceeded with a standard inversion that resulted in poor fit and unrealistic high resistivity in deeper layers in parts of the survey. Next, we inverted the data with a dispersive earth model, i.e. including the IP parameters. In the parts of the survey where the data could be fitted well with the “resistivity only” inversion the models changed minimally. In the remaining part, mostly with overly steep decays, the inverted models show chargeable, relatively shallow layers, the unrealistic high resistivity was not present anymore and in general, the data residuals dropped to be within the uncertainty of the data. We further analysed the data, specifically: 1) the sound-ings linked to chargeable areas; 2) the loss of information due to neglecting the negative or late time data with synthetic models; and 3) we explored the ability of the IP inversion models to recover the moderately chargeable layers. In conclusion, a large-scale airborne IP inversion was executed without any specific processing. Until now a time-consuming specific processing seemed to be a necessary step towards a successful IP inversion with airborne data.

KW - airborne TEM

KW - field data application

KW - induced polarization

KW - large-scale AEMIP inversion

UR - http://www.scopus.com/inward/record.url?scp=85090349891&partnerID=8YFLogxK

U2 - 10.1080/22020586.2019.12073088

DO - 10.1080/22020586.2019.12073088

M3 - Journal article

AN - SCOPUS:85090349891

VL - 2019

JO - Exploration Geophysics

JF - Exploration Geophysics

SN - 0812-3985

IS - 1

ER -