Deep structure of the northeastern margin of the Parnaiba Basin, Brazil, from magnetotelluric imaging

Mohamed, Adel K.; Meju, Max A.; Fontes, Sergio L.

doi:10.1046/j.1365-2478.2002.00338.x

Cited by 22 publications

(11 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We then corrected all the dual‐mode AMT and LMT apparent resistivity sounding curves for static‐shift arising from near‐surface heterogeneities using the dual‐configuration TEM data [e.g., Mohamed et al , 2002; Sakkas et al , 2002; Meju et al , 2003] as in the examples shown in Figure 3 (see Table 1 for all the correction factors), thus providing a stringent control of the level of MT apparent resistivities that is necessary for improved estimation of subsurface resistivity and interface depths. We recognize that this surface‐consistent static‐shift correction approach (weathering correction, sensu stricto) may not account for static‐shift arising from deeper small‐size 3‐D heterogeneities [e.g., Bahr et al , 2000].…”

Section: Reanalysis Of Broadband Mt Data From Southern Kenyamentioning

confidence: 99%

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

Meju

Sakkas

2007

J. Geophys. Res.

View full text Add to dashboard Cite

[1] We have used magnetotelluric data imaging to determine the resistivity structure across southern Kenya and our results suggest the presence of a buckled blocky or segmented lithosphere across the region. Prominent steep conductive zones at the Oloololo (OLO) escarpment and eastern rift margin allow us to subdivide the region into three crustal domains. West of OLO, a bow-shaped conductor underlies a 10 km thick resistive upper crustal unit spatially correlating with an exposed Archaean greenstone belt. Between OLO and the eastern rift margin are found steeply dipping alternating conductive and resistive zones that appear buckled. East of this belt are found prominent, 5 to 20 km deep, subhorizontal conductors atop steep resistive blocks with flanking conductors. The main steep features in the crust appear to extend below the seismic Moho and thus suggest the presence of anomalously thick crust across the region. A 50 km-wide and 4-8 km deep w-shaped (double half-graben) structure is suggested at the position of the Kenyan rift. We show that our inferred lateral zoning is consistent with collocated gravity and seismic measurements. We propose a link between the deep resistivity heterogeneity and surface deformation pattern in the area.

show abstract

Section: Reanalysis Of Broadband Mt Data From Southern Kenyamentioning

confidence: 99%

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

Meju

Sakkas

2007

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…We have reanalyzed some available field data comprising high‐quality collocated tensor MT and multigeometry TEM soundings along individual survey lines in different geological settings [ Meju , 1996; Danladi , 1997; Simpson et al , 1997; Meju et al , 1999; Mohamed et al , 2002; Sakkas et al , 2002] to gain some practical insight into possible geological and statistical constraints on static shifts and hence place the inverse problem within a robust geological framework. We sought to understand the pattern of variation of overburden resistivity and static shift with lithology at different spatial scales using soundings for which the station intervals ranged from 1 km (in a small‐scale survey) to 20 km (in a large‐scale regional survey).…”

Section: Introductionmentioning

confidence: 99%

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

Sasaki

Meju

2006

J. Geophys. Res.

View full text Add to dashboard Cite

[1] Accurate interpretation of magnetotelluric (MT) data in the presence of static shift arising from near-surface inhomogeneities is an unresolved problem in threedimensional (3-D) inversion. While it is well known in 1-D and 2-D studies that static shift can lead to erroneous interpretation, how static shift can influence the result of 3-D inversion is not fully understood and is relevant to improved subsurface analysis. Using the synthetic data generated from 3-D models with randomly distributed heterogeneous overburden and elongate homogeneous overburden that are consistent with geological observations, this paper examines the effects of near-surface inhomogeneity on the accuracy of 3-D inversion models. It is found that small-scale and shallow depth structures are severely distorted while the large-scale structure is marginally distorted in 3-D inversion not accounting for static shift; thus the erroneous near-surface structure does degrade the reconstruction of smaller-scale structure at any depth. However, 3-D joint inversion for resistivity and static shift significantly reduces the artifacts caused by static shifts and improves the overall resolution, irrespective of whether a zero-sum or Gaussian distribution of static shifts is assumed. The 3-D joint inversion approach works equally well for situations where the shallow bodies are of small size or long enough to allow some induction such that the effects of near-surface inhomogeneity are manifested as a frequency-dependent shift rather than a constant shift.Citation: Sasaki, Y., and M. A. Meju (2006), Three-dimensional joint inversion for magnetotelluric resistivity and static shift distributions in complex media,

show abstract

“…) and groundwater investigation (Sandberg ; Mohamed et al . ). In space constrained areas such as undulating mountains and coal mine fields, small‐loop instruments are preferred for TEM exploration since large loops are difficult to deploy.…”

Section: Introductionmentioning

confidence: 97%

Transient process and optimal design of receiver coil for small‐loop transient electromagnetics

Zhang

et al. 2013

Geophysical Prospecting

View full text Add to dashboard Cite

Distributed parameters of the receiver coils greatly affect transient electromagnetic signals over short time periods, causing a delay in the signal's effective sampling time and the loss of shallow exploration information. This paper investigates the influence of transient process on apparent resistivity calculation and analyses the relations between the error of apparent resistivity and receiver coil design. We find that, under the same effective area, different radii of the receiver coils lead to different levels of impact on the estimation of the apparent resistivity. An optimization model is proposed to determine the optimal receiver coil size that gives rise to the smallest estimation error of the apparent resistivity. The relationship between the optimal radius and the effective areas is developed, which serves as a guideline for the optimal receiver coil design. The results may provide a useful means for improving the accuracy of the small loop transient electromagnetic instrumentation for shallow‐depth mapping.

show abstract

Deep structure of the northeastern margin of the Parnaiba Basin, Brazil, from magnetotelluric imaging

Cited by 22 publications

References 13 publications

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

Heterogeneous crust and upper mantle across southern Kenya and the relationship to surface deformation as inferred from magnetotelluric imaging

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

Transient process and optimal design of receiver coil for small‐loop transient electromagnetics

Contact Info

Product

Resources

About