Three‐dimensional joint inversion for magnetotelluric resistivity and static shift distributions in complex media

Sasaki, Yutaka; Meju, Max A.

doi:10.1029/2005jb004009

Cited by 53 publications

(38 citation statements)

References 23 publications

(39 reference statements)

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“…Following this idea, several publications recommend inverting all four components of the MT impedance tensor (Z), for example Siripunvaraporn et al (2005b), Tietze & Ritter (2013) and Kiyan et al (2014), instead of the approach of inverting only the off-diagonal components (Z o ) (e.g. Sasaki 2004;Sasaki & Meju 2006). However, the presence of anthropogenic noise can strongly reduce the quality of the Z data, in particular the quality of the diagonal components, making it sometimes worthless to use all components of the Z tensor for the inversion process because of scatter and/or extremely large errors in the diagonal components of Z.…”

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confidence: 99%

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Campanyà¹,

Ogaya²,

Jones³

et al. 2016

Geophys. J. Int.

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: The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study. -Geophysical Journal International, 207, 3, pp. 1818-1836 S U M M A R YAs a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in 2-D and 3-D environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomalies surrounding the acquisition site. This behaviour complicates the characterization of the electrical resistivity distribution of the subsurface, particularly in complex areas. In this manuscript we assess the main advantages of complementing the standard MT impedance tensor (Z) data with interstation horizontal magnetic tensor (H) and geomagnetic transfer function (T) data in constraining the subsurface in a 3-D environment beneath a MT profile. Our analysis was performed using synthetic responses with added normally distributed and scattered random noise. The sensitivity of each type of data to different resistivity anomalies was evaluated, showing that the degree to which each site and each period is affected by the same anomaly depends on the type of data. A dimensionality analysis, using Z, H and T data, identified the presence of the 3-D anomalies close to the profile, suggesting a 3-D approach for recovering the electrical resistivity values of the subsurface. Finally, the capacity for recovering the geoelectrical structures of the subsurface was evaluated by performing joint inversion using different data combinations, quantifying the differences between the true synthetic model and the models from inversion process. Four main improvements were observed when performing joint inversion of Z, H and T data: (1) superior precision and accuracy at characterizing the electrical resistivity values of the anomalies below and outside the profile; (2) the potential to recover high electrical resistivity anomalies that are poorly recovered using Z data alone; (3) improvement in the characterization of the bottom and lateral boundaries of the anomalies with low electrical resistivity; and (4) superior imaging of the horizontal continuity of structures with low electrical resistivity. These advantages offer new opportunities for the MT method by making the results from a MT profile in a 3-D environment more convincing, supporting the possibility of high-resolution studies in 3-D areas without expending a large amount of economical and computational resources, and also offering better resolution of targets with high electrical resistivity.

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confidence: 99%

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Campanyà¹,

Ogaya²,

Jones³

et al. 2016

Geophys. J. Int.

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“…However, the phase tensor is only a partial solution; thus, the inverted model strongly depends on the initial model (Patro et al 2013;Tietze et al 2015). In addition to decomposition approaches, inversion schemes that simultaneously solve the static shift (e.g., Sasaki and Meju 2006) have become feasible, but the geometric distortion is not controlled. Avdeeva et al (2015) proposed 3D inversion with the solution of the full distortion matrix, but this approach does not allow this static shift to be a free parameter.…”

Section: )mentioning

confidence: 99%

“…In addition, the employment of these two types of properties allows the effect of the site gain to be separated from the effects of the twist, shear, and splitting parameters. Most importantly, we can use these parameters to determine the necessary treatment of galvanic distortion for a given dataset, such as whether or not a removal scheme should be applied in the inversion (e.g., Sasaki and Meju 2006;Avdeeva et al 2015).…”

Section: )mentioning

confidence: 99%

Use of ssq rotational invariant of magnetotelluric impedances for estimating informative properties for galvanic distortion

Rung-Arunwan

Siripunvaraporn

Utada

2017

Earth Planets Space

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Several useful properties and parameters-a model of the regional mean one-dimensional (1D) conductivity profile, local and regional distortion indicators, and apparent gains-were defined in our recent paper using two rotational invariants (det: determinant and ssq: sum of squared elements) from a set of magnetotelluric (MT) data obtained by an array of observation sites. In this paper, we demonstrate their characteristics and benefits through synthetic examples using 1D and three-dimensional (3D) models. First, a model of the regional mean 1D conductivity profile is obtained using the average ssq impedance with different levels of galvanic distortion. In contrast to the Berdichevsky average using the average det impedance, the average ssq impedance is shown to yield a reliable estimate of the model of the regional mean 1D conductivity profile, even when severe galvanic distortion is contained in the data. Second, the local and regional distortion indicators were found to indicate the galvanic distortion as expressed by the splitting and shear parameters and to quantify their strengths in individual MT data and in the dataset as a whole. Third, the apparent gain was also shown to be a good approximation of the site gain, which is generally claimed to be undeterminable without external information. The model of the regional mean 1D profile could be used as an initial or a priori model in higher-dimensional inversions. The local and regional distortion indicators and apparent gains could be used to examine the existence and to guess the strength of the galvanic distortion. Although these conclusions were derived from synthetic tests using the Groom-Bailey distortion model, additional tests with different distortion models indicated that these conclusions are not strongly dependent on the choice of distortion model. These galvanic-distortion-related parameters would also assist in judging if a proper treatment is needed for the galvanic distortion when an MT dataset is given. Hence, this information derived from the dataset would be useful in MT data analysis and inversion.

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“…5) show a possible static shift and/or topographic effects at sites 4, 5, 16, 17, 18, and 27. The model could be compensated by these static shift data at shallow depth to incorporate nearsurface structure (Sasaki 2004), which indicates that the inverted model is still fine at deep depth in the inversion (e.g., Sasaki and Meju 2006). The 3D inversion code can only invert impedances and it is thus impossible to assign different error floors to apparent resistivity and phase as in typical 2D inversions.…”

Section: D Inversionmentioning

confidence: 99%

An Investigation of the 3D Electrical Resistivity Structure in the Chingshui Geothermal Area, NE Taiwan

Chiang¹,

Hsu²,

Chen³

2015

Terr. Atmos. Ocean. Sci.

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The Chingshui geothermal area southwest of the Ilan plain is identified as a western extension of the Okinawa Trough in the northern Taiwan subduction system. Numerous geophysical, geological and geochemical investigations have been conducted since the 1970s by the Industrial Technology Research Institute, the Chinese Petroleum Corporation of Taiwan and the National Science Council of Taiwan. These studies indicated that the Chingshui stream is one of the largest geothermal areas for electricity generation in Taiwan. However, the power generation efficiency has not met initial expectations. Magnetotelluric (MT) data analyses show that the Chingshui geothermal region is a geologically complex area. A full three-dimensional (3D) inversion was therefore applied to reprocess the MT data and provide the detailed electrical structure beneath the Chingshui geothermal region. The 3D geoelectrical model displays an improved image that clearly delineates the Chingshui geothermal system geometry. Two conductive anomalies are imaged that possibly indicate high potential areas for geothermal energy in the Chingshui geothermal system. One of the potential areas is located in the eastern part of the Chingshui Fault at shallow depths. A significant conductive anomaly is associated with high heat flow and fluid content situations southwest of the geothermal manifest area at depth. A higher interconnected fluid indicates that this area contains the highest potential for geothermal energy in the Chingshui geothermal system.

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Three‐dimensional joint inversion for magnetotelluric resistivity and static shift distributions in complex media

Cited by 53 publications

References 23 publications

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Use of ssq rotational invariant of magnetotelluric impedances for estimating informative properties for galvanic distortion

An Investigation of the 3D Electrical Resistivity Structure in the Chingshui Geothermal Area, NE Taiwan

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