Imaging and observing the electrical Moho

Jones, Alan G.

doi:10.1016/j.tecto.2013.02.025

Cited by 39 publications

(18 citation statements)

References 81 publications

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“…During initial inversion steps, four tear zones were applied to maintain separation of the model into upper (0–10 km), intermediate (10–24km), and lower crust (24–31.5km) as well as the mantle (≥31.5km) (Note, a tear zone is where changes in conductivity across the boundary do not contribute to the summed roughness measure so can be as discontinuous in conductivity as required to best fit the data. An example is shown for 1‐D in Jones [] where a tear zone was permitted at the Moho, analogous to what we are doing here);…”

Section: Inversionmentioning

confidence: 68%

“…The subsequent steps that were followed were as follows: During initial inversion steps, four tear zones were applied to maintain separation of the model into upper (0–10 km), intermediate (10–24km), and lower crust (24–31.5km) as well as the mantle (≥31.5km) (Note, a tear zone is where changes in conductivity across the boundary do not contribute to the summed roughness measure so can be as discontinuous in conductivity as required to best fit the data. An example is shown for 1‐D in Jones [] where a tear zone was permitted at the Moho, analogous to what we are doing here); Features were manually removed or their resistivity values were modified in order to test whether they became reestablished in subsequent inversion steps and could therefore be considered data‐supported structures; Focused inversions were carried out for specific regions of the subsurface by individually inverting responses from selected stations; Anisotropic 2‐D inversions, using the code of Baba et al [], were carried out using a range of isotropy parameters ( τ iso ) in order to test for the existence of possible anisotropic structures.…”

Section: Inversionmentioning

confidence: 99%

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Structures and geometries of the Tajo Basin crust, Spain: Results of a magnetotelluric investigation compared to seismic and thermal models

2014

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The Tajo Basin and Betic Mountain Chain in the south central region of the Iberian Peninsula were chosen for investigation in the first phase of the magnetotelluric (MT) component of the PICASSO (Program to Investigate the Convective Alboran Sea System Overturn) project. The MT results provide information about the electrical conductivity distribution in previously unprobed subsurface regions, as well as complimenting and enhancing results of prior geological and geophysical investigations thereby enabling the definition of a petrological subsurface model and a comprehensive understanding about the tectonic setting. Two‐dimensional (2‐D) inversion of the MT data provides enhanced insight into Iberian subsurface geology in the crust. The most striking features of the final model are (i) a distinct vertical interface within the Variscan basement beneath the center of the Tajo Basin that is spatially associated with the boundary between regions with and without substantial Alpine deformation, and (ii) a middle to lower crustal conductive anomaly that can be related to remnants of asthenospheric intrusion in connection with Pliocene volcanic events in the Calatrava Volcanic Province. For the latter, effects of hydrous phases are inferred that may originate from dehydration processes within the subducting slab beneath Alboran Domain and Betic Mountain Chain.

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Section: Inversionmentioning

confidence: 68%

Section: Inversionmentioning

confidence: 99%

Structures and geometries of the Tajo Basin crust, Spain: Results of a magnetotelluric investigation compared to seismic and thermal models

2014

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“…They also provide insight into conductors observed within Archean cratons ) and infer plate tectonic processes somewhat similar to those observed today. • One of the seminal results of the Lithoprobe magnetotelluric studies was the first definitive observation of the electrical conductivity structure of the Moho Jones 2013). This observation was enabled by the absence in the Mesoarchean crust of the southeast Slave Craton of any enhancement of conductivity in the middle to lower crust.…”

Section: Results With Global Consequencesmentioning

confidence: 99%

The electrical resistivity of Canada’s lithosphere and correlation with other parameters: contributions from Lithoprobe and other programmes

et al. 2014

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Over the last 30 years, through Lithoprobe and other programmes, modern, high-quality magnetotelluric (MT) measurements probing deep into the lithosphere and underlying asthenosphere have been made at over 6000 sites across Canada in all provinces and territories, except Nova Scotia. Some regions are well covered, particularly Alberta, southern British Columbia, and western Ontario, whereas others remain poorly covered, such as Quebec and large swaths of Nunavut. Prior publications from individual studies have added significantly to the wealth of Canada's geoscience knowledge, and have demonstrated that MT can contribute significantly to understanding of the tectonic processes that have shaped Canada. However, to date no continent-scale maps of lithospheric electrical parameters have been constructed from the extensive MT database. Herein we review the contributions made by the MT components of Lithoprobe, and present new continental-scale maps of various electrical parameters at crustal and upper mantle depths for the whole of Canada. From those maps, combined with regional estimates of temperature, we develop derivative information on petrological-geophysical properties, including predictions of temperature and water content. We find that at 100 km depth the Canadian Shield is cold and dry, and the Cordillera is warmer but mostly dry, i.e., little water is present in the peridotite. Exceptions are beneath the Prairies, the Wopmay Orogen, and northeast Nunavut where there does appear to be water in the nominally anhydrous minerals. Also, southwest British Columbia appears colder than the rest of the Cordillera due to the subducting Juan de Fuca plate. In contrast, at 200 km depth almost all of Canada is dry.Résumé : Au cours des trente dernières années, grâce à Lithoprobe et à d'autres programmes, des mesures magnétotelluriques (MT), modernes et de grande qualité, ont été prises à plus de 6000 sites à travers le Canada, dans toutes les provinces et territoires sauf en Nouvelle-Écosse; ces mesures sondaient profondément dans la lithosphère et l'asthénosphère sous-jacente. Certaines régions sont bien couvertes, surtout l'Alberta, le sud de la Colombie-Britannique et l'ouest de l'Ontario, alors que d'autres sont mal couvertes, par exemple le Québec et de grandes parties du Nunavut. Des publications antérieures, basées sur des études individuelles, ont grandement contribué à enrichir les connaissances géoscientifiques canadiennes et elles ont démontré que les mesures MT peuvent grandement contribuer à la compréhension des processus tectoniques qui ont formé le Canada. Toutefois, à ce jour, aucune carte des paramètres électriques lithosphériques, à l'échelle du continent, n'a été construite à partir de la vaste base de données MT. Dans le présent article, nous revoyons les contributions des composantes MT de Lithoprobe et nous présentons de nouvelles cartes à l'échelle du continent de divers paramètres électriques aux profondeurs de la croûte et du manteau supérieur pour l'ensemble du Canada. À partir de ces cartes, ...

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“…Thus, in this section, the second aim is to examine how the algorithm behaves if we are inverting for velocity parameters and interface depth simultaneously. Note that an electric Moho is not defined here because it is difficult to resolve in most localities (Jones, ). Our joint inversion approach can be a contributing way to determine the exact electric Moho, but prior to the use it should be primarily established that there is an acceptable expectation of an electric Moho from the MT data.…”

Section: Synthetic Examples and Discussionmentioning

confidence: 99%

Structure‐Coupled 3‐D Imaging of Magnetotelluric and Wide‐Angle Seismic Reflection/Refraction Data With Interfaces

2019

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Magnetotelluric (MT) and wide-angle seismic reflection/refraction surveys play a fundamental role in understanding the crustal rheology and lithospheric structure of the Earth. In recent years, the integration of the two methods in order to improve the robustness of the inversion has started to gain attention. We present a new approach for joint 3-D inversion of MT and wide-angle seismic reflection/refraction data to accurately determine crustal structures and Moho depth. Based on H-κ stacking of teleseismic receiver functions, we estimate an initial reference Moho. This is used as input for the subsequent MT/seismic joint inversion, where the Moho interface is updated and crustal structures are added to the model. During the joint inversion process, structural similarity is facilitated through the cross-gradient constraint. Synthetic model tests show an improvement of the inversion results over separate inversions. In particular, the tests based on two geologically realistic models demonstrate that the crustal structure and even the trade-off between velocity and Moho interface can be sufficiently resolved by combined MT and seismic data sets when using the estimates from analysis of receiver functions. These results show that the new method can provide useful constraints on crustal structures including their geophysical properties and discontinuities.

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Imaging and observing the electrical Moho

Cited by 39 publications

References 81 publications

Structures and geometries of the Tajo Basin crust, Spain: Results of a magnetotelluric investigation compared to seismic and thermal models

Structures and geometries of the Tajo Basin crust, Spain: Results of a magnetotelluric investigation compared to seismic and thermal models

The electrical resistivity of Canada’s lithosphere and correlation with other parameters: contributions from Lithoprobe and other programmes

Structure‐Coupled 3‐D Imaging of Magnetotelluric and Wide‐Angle Seismic Reflection/Refraction Data With Interfaces

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