A two-dimensional magnetotelluric inversion assuming Gaussian static shift

Ogawa, Yasuo; Uchida, Toshihiro

doi:10.1111/j.1365-246x.1996.tb05267.x

Cited by 165 publications

(87 citation statements)

References 15 publications

(20 reference statements)

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“…de Groot-Hedlin (1991) suggested that static shifts may be treated as unknown free parameters during inversion. Also, Gaussian distributions of the static shifts (Ogawa and Uchida, 1996) are assumed. This is a very simple, but reasonable assumption because the static shifts in the data are assumed normally distributed and these distributions have a central mean and well-estimated variance.…”

Section: Mt Data Acquisition and Processingmentioning

confidence: 99%

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

Adepelumi

Fontes

Schnegg

et al. 2005

Physics of the Earth and Planetary Interiors

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The research is aimed at delineating the post-impact structural characteristics across the Serra da Cangalha impact crater in Brazil using a combination of magnetotelluric (MT) and aeromagnetic data. The MT survey was carried out along three radial MT profiles trending NW-SE, ENE-WSW and NNE-SSW across the crater. For MT sites located further away from the centre of the crater, isotropic MT responses were observed, suggesting a 1D conductivity distribution in the subsurface in the frequency range of 100-10 Hz. For sites located in the vicinity of the inner ring of the crater, anisotropic responses were observed for the same frequency range. We believe that this zone probably represents the areas of structural disturbance. A 2D resistivity inversion of these data reveals a four-layer model, representing a thin resistive layer underlain by a conductive layer, a weathered basement and a resistive crystalline basement. The depth to the top of the basement is estimated to be about 1.2 km. This is in good agreement with the estimation of depth to the basement of about 1.1 km, calculated using the aeromagnetic data. However, in view of the circular geometry of the crater, we have carried out a 3D forward modeling computation to supplement the derived 2D model. The 3D resistivity forward model, fitting the MT responses by trial-by-error revealed a five-layer model, showing a significant reduction in the basement resistivity. This, perhaps, could be due to the structural disturbances that have been caused by the impact on the crater, resulting in brecciation, fracturing, alteration and shocked zone filled with weak-magnetic materials and fluids. We have calculated the effect of the impact on the overall structural deformation beneath the Serra da Cangalha crater, following the classical crater scaling relation of Holsapple and Schmidt [Holsapple, K.A., Schmidt, R.M., 1982

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Section: Mt Data Acquisition and Processingmentioning

confidence: 99%

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

Adepelumi

Fontes

Schnegg

et al. 2005

Physics of the Earth and Planetary Interiors

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“…In this study, a two-dimensional inversion was conducted with two types of constraints similar to Ogawa and Uchida (1996). One type is model roughness norm, and the other is static shift L2 norm.…”

Section: Resultsmentioning

confidence: 99%

“…A two-dimensional inversion was applied to the TM mode data (Z.,,y), based on the work of Ogawa and Uchida (1996) and Ogawa (1997). An outline of the idea is described below.…”

Section: Two-dimensional Inversion Schemementioning

confidence: 99%

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Data-Adaptive Inversion of the Oklahoma EMAP Dataset.

Ogawa

1997

J. geomagn. geoelec

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The Oklahoma EMAP dataset was analyzed using a two-dimensional inversion algorithm which includes static shifts as free parameters. Model misfit was minimized while simultaneously minimizing the resistivity roughness norm and the static shift L2 norm. The tradeoff parameters between the model misfit and these two norms were determined to minimize the Akaike's Bayesian Information Criterion (ABIC).

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“…We included static shifts as model parameters in addition to the model resistivity (Ogawa and Uchida, 1996). The misfit was minimized under the two constraints; one is the Laplacian model roughness and the other is static shift L2 norm.…”

Section: Two-dimensional Modelingmentioning

confidence: 99%

Preliminary Magnetotelluric Modeling in the Nikko Volcanic Area. Potential Break of Fluid Trap by Volcanic Intrusion.

Ogawa

Honkura

Ohtani

et al. 1997

J. geomagn. geoelec

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We collected magnetotelluric data in the Nikko volcanic area in the period range from 0.01 to 10 sec. Impedance data were decomposed with the regional strike direction N0°E and were analized by two-dimensional inversions including static shifts as model parameters. The major model features are: (1) southern conductor at 8 km depth which is consistent with the seismic S-wave reflectors, (2) northern conductor located at 5 km depth, consistent with the seismic attenuation zones, and (3) a resistitive gap in between, consistent with the magnetic body inferred from aeromagnetic data. The two conductors probably imply trapped free water at around 400°C. The resistor in between implies the volcanic body, which intruded the crust and may have broken the regime of trapped free water.

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A two-dimensional magnetotelluric inversion assuming Gaussian static shift

Cited by 165 publications

References 15 publications

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

Data-Adaptive Inversion of the Oklahoma EMAP Dataset.

Preliminary Magnetotelluric Modeling in the Nikko Volcanic Area. Potential Break of Fluid Trap by Volcanic Intrusion.

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