Continental-scale deep electrical resistivity structure beneath China

Yuan, Yiren; Uyeshima, Makoto; Huang, Qinghua; Tang, Ji; Li, Qi; Teng, Yuntian

doi:10.1016/j.tecto.2020.228559

Cited by 12 publications

(9 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since the amplitude of the vertical magnetic field is generally reduced for a more conductive Earth (39), sites with negative misfits suggest a more conductive underlying mantle and vice versa. The misfit plot thus suggests a more conductive mantle beneath the North China Craton than the Indian Shield, which is consistent with the high-and low-conductivity anomalies beneath eastern China and western Yangtze Craton adjoining the Indian Shield, respectively (22). The coherent spatial pattern in the signed misfit implies that there are strong lateral variations in the upper and mid-mantle conductivity.…”

Section: Discussionsupporting

confidence: 73%

“…Given the high sensitivity of electrical conductivity to the concentration of hydrogen in mantle minerals (6,17), reliable estimates of this physical parameter could provide valuable constraints on water content. Measurements of natural variations of geomagnetic fields, due to ionospheric and magnetospheric current systems that induce image currents deep in Earth, can be used to infer mantle electrical conductivity (18)(19)(20)(21)(22). These magnetovariational induction methods, which require accurate models of the external source fields, have been most successfully applied to long-period (> 2 day) disturbance storm time (Dst) variations, since their source can be reasonably modeled by a relatively simple magnetospheric ring current (18).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A relatively dry mantle transition zone revealed by geomagnetic diurnal variations

2022

Self Cite

View full text Add to dashboard Cite

The distribution of water within the mantle transition zone (MTZ) has important implications for the material circulation and partial melting of the mantle. Although solubility of hydrogen is very high, leading to speculations that the MTZ plays a key role in the deep-Earth water cycle, the actual water content remains an open question. Electrical conductivity of mantle minerals is very sensitive to water content, so reliable estimates of this physical parameter in the MTZ would provide valuable constraints. Here, we use recently developed joint inversion of geomagnetic diurnal variation for realistic source structure and one-dimensional mantle conductivity profile. Synthetic tests show that the resulting profile is a reasonable proxy for the electrical conductivity distribution of continental mantle over depths where model resolution is best (200 to 600 kilometer), even in the presence of lateral heterogeneity. The inferred water concentration in the MTZ is 0.03 weight %, one to two orders of magnitude below the solubility of wadsleyite and ringwoodite.

show abstract

Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

A relatively dry mantle transition zone revealed by geomagnetic diurnal variations

2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Using the multi‐resolution finite element modeling tool, we have systematically investigated the local ocean effects for several unused coastal observatories in southeast China, which were excluded from previous global EM studies (Yuan et al., 2020). Although different mesh resolutions are needed for different observatories, our model studies indicated that at least for coastal observatories in China, a mesh with 1° angular resolution is adequate for accurately modeling the local ocean effects.…”

Section: Interpretation Of Chinese Coastal Geomagnetic Observatory Datamentioning

confidence: 99%

“…Recently, the coastal geomagnetic data in northeast China have been used to constrain the mantle electrical conductivity and water content (Y. Zhang et al., 2020). However, several coastal geomagnetic observatories in southeast China (such as Quanzhou and Yongning observatories) are not used for mantle conductivity imaging (Yuan et al., 2020) due to the lack of accurately accounting for the strong local ocean effects.…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al, 2020). However, several coastal geomagnetic observatories in southeast China (such as Quanzhou and Yongning observatories) are not used for mantle conductivity imaging (Yuan et al, 2020) due to the lack of accurately accounting for the strong local ocean effects. We now apply our multi-resolution finite element approach to guide the interpretation of the southeast China coastal observatory data.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Multi‐Resolution Finite‐Element Approach for Global Electromagnetic Induction Modeling With Application to Southeast China Coastal Geomagnetic Observatory Studies

et al. 2022

View full text Add to dashboard Cite

We present a multi‐resolution finite‐element approach for three‐dimensional (3D) electromagnetic (EM) induction modeling in spherical Earth. First, the secondary electric field approach is employed so that both magnetospheric and ionospheric current sources are naturally considered. Second, the multi‐resolution tetrahedral grids are used to approximate the heterogeneous crust and mantle, so that the local ocean effects at coastal and island observatories can be accurately simulated. Furthermore, a parallel goal‐oriented hp‐adaptive finite‐element method with Nédélec vector elements is employed to guarantee the accuracy of solutions for arbitrary 3D conductivity distributions. Finally, two synthetic models are used to verify the accuracy and efficiency of our newly developed forward modeling solver. Results show that accurate solutions can be obtained for problems with several million to hundreds of millions of unknowns in a few minutes using 128 cores on a cluster. We apply this approach to correct the near‐surface ocean effects for several unused Chinese coastal observatories by performing multi‐resolution 3D modeling. The corrected data are inverted for the subsurface layered mantle conductivity structures. The conductivity model beneath southeast China is more resistive than that beneath northeast China by more than half an order of magnitude. By comparing the inverse models with the latest laboratory conductivity‐depth profiles, the estimated transition zone water content is less than 0.01 wt% beneath southeast China irrespective of which laboratory data is used. Considering the low‐velocity anomalies in this region, which suggest high‐temperature structures, less water is expected. We, therefore, infer that the mantle transition zone beneath southeast China is dry.

show abstract

Unravelling the Electrical Conductivity of Earth and Planets

Grayver

2024

Surv Geophys

View full text Add to dashboard Cite

This review presents the progress made in the last decade in the field of large-scale electromagnetic (EM) induction with natural sources, which fluctuate at periods from seconds to years and originate in oceans, ionosphere and magnetosphere. These mechanisms produce field variations that can be used to image subsurface electrical structure of Earth and planets across scales and depths from the shallow crust to the lower mantle. In the last decade, we have seen a substantial progress made in different areas related to methods, observations and 3-D numerical modelling of EM phenomena at crustal and mantle scales. Specifically, new methods for handling complex ionospheric and magnetospheric sources were proposed, accompanied by more efficient forward and inverse modelling tools that allowed us to combine several broadband sources and constrain electrical conductivity on multiple scales simultaneously. Magnetic signals due to oceanic tides were established as a new source to probe conductivity of the sub-oceanic upper mantle. Further, the launch of ESA Swarm satellites in 2013 and their successful ongoing operation have marked a new era in the field of large-scale EM induction, unlocking a set of new opportunities, but also posing new challenges. These developments were backed by new lab measurements of electrical conductivity for mantle minerals at temperatures and pressures that are getting closer to the relevant pressure and temperature conditions in the mantle, alleviating the need for inaccurate extrapolations. The latter enabled more plausible quantitative estimates of water content, melt fractions and temperature in the mantle. In parallel, crust and mantle conductivity models along with developed modelling techniques have become an integral part of geomagnetic field and geomagnetically induced currents (GICs) modelling workflows, establishing new inter-disciplinary knowledge domains.

show abstract

Continental-scale deep electrical resistivity structure beneath China

Cited by 12 publications

References 43 publications

A relatively dry mantle transition zone revealed by geomagnetic diurnal variations

A relatively dry mantle transition zone revealed by geomagnetic diurnal variations

A Multi‐Resolution Finite‐Element Approach for Global Electromagnetic Induction Modeling With Application to Southeast China Coastal Geomagnetic Observatory Studies

Unravelling the Electrical Conductivity of Earth and Planets

Contact Info

Product

Resources

About