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Reframing the magnetotelluric phase tensor for monitoring applications: improved accuracy and precision in strike determinations.
Ana Gabriela Bravo-Osuna
Centro de Investigacion Cientifica y de Educacion Superior de Ensenada
Corresponding Author
ORCiD: https://orcid.org/0000-0002-6848-2806
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published version at Earth, Planets and Space.
The magnetotelluric method is increasingly being used to monitor electrical resistivity changes in the subsurface. One of the preferred parameters derived from the surface impedance is the strike direction, which is very sensitive to changes in the direction of the subsurface electrical current flow. The preferred method for estimating the strike changes is that provided by the phase tensor because it is immune to galvanic distortions. However, it is also a fact that the associated analytic formula is unstable for noisy data, something that limits its applicability for monitoring purposes, because in general this involves comparison of two or more very similar data sets. One of the issues is that the noise complicates the distribution of estimates between the four quadrants. This can be handled by sending all values to the same quadrant by adding or subtracting the appropriate amount. This is justified by showing that the analytic formula is also a least squares solution. This is equivalent to define penalty functions for the matrix of eigenvalues and then select the minima numerically. Contrary to the analytic formula this numerical approach can be generalized to compute strikes using windows of any number of periods, thus providing tradeoffs between variance and resolution. The performance of the proposed approach is illustrated by its application to synthetic data and to real data from a monitoring array in the Cerro Prieto geothermal field, México.
Keywords
Magnetotelluric monitoring, Phase tensor, Swift strike, Galvanic distortion
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On 01 Jan, 2021
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Received 12 Dec, 2020
Editorial decision: Minor Revision
On 12 Dec, 2020
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Reviewer #1 agreed
On 11 Nov, 2020
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Editorial decision: Major Revision
On 26 Sep, 2020
Review #1 received
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Received 06 Sep, 2020
Reviewer #2 agreed
On 24 Aug, 2020
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On 23 Aug, 2020
Editor assigned
On 22 Aug, 2020
Reviewers invited
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Submission checks complete
On 21 Aug, 2020
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Editorial decision: Major Revision
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Review #2 received
Received 06 Jul, 2020
Review #1 received
Received 15 May, 2020
Reviewer #2 agreed
On 05 May, 2020
Editor assigned
On 23 Apr, 2020
Reviewers invited
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Reviewer #1 agreed
On 23 Apr, 2020
Editor invited
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Subject Areas
Geology
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This preprint is under consideration at Earth, Planets and Space. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Full paper
Reframing the magnetotelluric phase tensor for monitoring applications: improved accuracy and precision in strike determinations.
Ana Gabriela Bravo-Osuna
Centro de Investigacion Cientifica y de Educacion Superior de Ensenada
Corresponding Author
ORCiD: https://orcid.org/0000-0002-6848-2806
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
Version 4
Posted 12 Jan, 2021
Published
On 02 Feb, 2021
No community comments so far
Editor assigned
On 01 Jan, 2021
Editorial decision: Accept
On 01 Jan, 2021
Submission checks complete
On 01 Jan, 2021
Editor invited
On 01 Jan, 2021
No comments provided
Review #1 received
Received 12 Dec, 2020
Editorial decision: Minor Revision
On 12 Dec, 2020
Reviewers invited
Invitations sent on 11 Nov, 2020
Reviewer #1 agreed
On 11 Nov, 2020
Editor assigned
On 10 Nov, 2020
Submission checks complete
On 10 Nov, 2020
Editor invited
On 10 Nov, 2020
No comments provided
Editorial decision: Major Revision
On 26 Sep, 2020
Review #1 received
Received 25 Sep, 2020
Review #2 received
Received 06 Sep, 2020
Reviewer #2 agreed
On 24 Aug, 2020
Reviewer #1 agreed
On 23 Aug, 2020
Editor assigned
On 22 Aug, 2020
Reviewers invited
Invitations sent on 22 Aug, 2020
Submission checks complete
On 21 Aug, 2020
Editor invited
On 21 Aug, 2020
No comments provided
Editorial decision: Major Revision
On 07 Jul, 2020
Review #2 received
Received 06 Jul, 2020
Review #1 received
Received 15 May, 2020
Reviewer #2 agreed
On 05 May, 2020
Editor assigned
On 23 Apr, 2020
Reviewers invited
Invitations sent on 23 Apr, 2020
Reviewer #1 agreed
On 23 Apr, 2020
Editor invited
On 22 Apr, 2020
Submission checks complete
On 18 Apr, 2020
First submitted
On 17 Apr, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Geology
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published version at Earth, Planets and Space.
The magnetotelluric method is increasingly being used to monitor electrical resistivity changes in the subsurface. One of the preferred parameters derived from the surface impedance is the strike direction, which is very sensitive to changes in the direction of the subsurface electrical current flow. The preferred method for estimating the strike changes is that provided by the phase tensor because it is immune to galvanic distortions. However, it is also a fact that the associated analytic formula is unstable for noisy data, something that limits its applicability for monitoring purposes, because in general this involves comparison of two or more very similar data sets. One of the issues is that the noise complicates the distribution of estimates between the four quadrants. This can be handled by sending all values to the same quadrant by adding or subtracting the appropriate amount. This is justified by showing that the analytic formula is also a least squares solution. This is equivalent to define penalty functions for the matrix of eigenvalues and then select the minima numerically. Contrary to the analytic formula this numerical approach can be generalized to compute strikes using windows of any number of periods, thus providing tradeoffs between variance and resolution. The performance of the proposed approach is illustrated by its application to synthetic data and to real data from a monitoring array in the Cerro Prieto geothermal field, México.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Due to technical limitations, full-text HTML conversion of this manuscript could not be completed. However, the latest manuscript can be downloaded and accessed as a PDF.