Electrical conductivity images of active and fossil fault zones

Ritter, O.; Hoffmann‐Rothe, A.; Bedrosian, Paul A.; Weckmann, U.; Haak, V.

doi:10.1144/gsl.sp.2005.245.01.08

Cited by 69 publications

(59 citation statements)

References 85 publications

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“…Ritter et al 2003Ritter et al , 2005Unsworth & Bedrosian 2004;Tank et al 2005;Thiel et al 2009;Becken et al 2011;Desissa et al 2013). The geometry and the overall conductance of FZCs depend on local geological, hydrogeological conditions and the geodynamic (tectonic) setting of a fault (see Unsworth & Bedrosian 2004;Ritter et al 2005, and references therein.). Ritter et al (2003) interpreted MT data collected along a profile across the Araba fault (a segment of the DST) which is located ∼150 km to the south of the DSB.…”

Section: Discussion O F T H E 2 -D E L E C T R I C a L C O Nmentioning

confidence: 99%

“…5 is likely linked to shear deformation of the DST in the middle and lower crust and related processes. High conductivities in active tectonic zones have often been associated with fluids and hydrous minerals (Boerner et al 1998;Unsworth & Bedrosian 2004;Jones et al 2005;Ritter et al 2005;Wannamaker 2005;Becken et al 2011;Meqbel et al 2014). For instance, Becken et al (2011) interpreted a subvertical conductive anomaly extending through the entire crust northwest of Parkfield in California as a migration path for deep (partly mantle derived) fluids into the San Andreas Fault system.…”

Section: Discussion O F T H E 2 -D E L E C T R I C a L C O Nmentioning

confidence: 99%

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Crustal metamorphic fluid flux beneath the Dead Sea Basin: constraints from 2-D and 3-D magnetotelluric modelling

et al. 2016

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S U M M A R YWe report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike-slip Dead Sea transform (DST) fault splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2-D inversion model is a deep, subvertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid-to low-grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the DSB and the high subsidence rate of basin sediments. 3-D inversion models confirm the existence of a subvertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3-D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3-D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3-D model furthermore contains an E-W elongated conductive structure to the northeast of the DSB. More MT data with better spatial coverage are required, however, to fully constrain the robustness of the above-mentioned off-profile features.

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Section: Discussion O F T H E 2 -D E L E C T R I C a L C O Nmentioning

confidence: 99%

Section: Discussion O F T H E 2 -D E L E C T R I C a L C O Nmentioning

confidence: 99%

Crustal metamorphic fluid flux beneath the Dead Sea Basin: constraints from 2-D and 3-D magnetotelluric modelling

et al. 2016

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“…fault zones providing pathways for fluids, lubricating the system and adding to its mobility (e.g. Ritter et al, 2005). Even if the fluids have escaped over time, the mineral phases left behind often retain high conductivities and maintain the mobility of the system.…”

Section: Introductionmentioning

confidence: 99%

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Weckmann

2011

Surv Geophys

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The African continent inherits a long history of continental accretion and breakup. The stage of "making" a continent goes back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation of supercontinents. After the assemblage of Gondwana, a period of predominantly "breaking" , i.e. the breakup of supercontinents, took over. The modern day African continent exhibits different types of margins; continental rifting occurs side by side with recent collision. Since the late 1960's Magnetotelluric (MT) experiments have played an important role in studies of the electrical conductivity structure of Africa. The early results significantly shaped the MT community's understanding of continental scale conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scale for some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted in higher resolution images of the lithosphere which in consequence induce an improved understanding of tectonic processes and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today's margins does not allow for good resolution of remnants of continental break-up processes. Naturally, the regions and the focus of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent.

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“…Images of the subsurface electrical conductivity structure of fault zones can be used to overcome this problem. Several published results demonstrate the successful application of the magnetotelluric (MT) method for studying fault-related structures and their geometry at depth [e.g., Ritter et al, 2004Ritter et al, , 2003Bedrosian et al, 2002;Wannamaker et al, 2002;Hoffmann-Rothe et al, 2001;Unsworth and Bedrosian, 2004;Unsworth et al, 2000Unsworth et al, , 1999Unsworth et al, , 1997Jones, 1998;Mackie et al, 1997]. Particularly, the work on the conductivity structure of segments of the San Andreas Fault in California exemplifies the existence of fault-related subsurface anomalies of high conductivity, socalled fault zone conductors (FZC).…”

Section: Introductionmentioning

confidence: 99%

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

2004

Self Cite

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[1] Large-scale strike-slip fault zones are often imaged as electrically conductive structures in the brittle crust. However, the relationship of conductivity and internal architecture of the fault zone remains largely unclear. This paper presents results of a study designed to compare the record of structural deformation across a fault zone with its electrical conductivity image. Two high-resolution magnetotelluric profiles trend perpendicularly across the West fault, a branch of the Precordilleran fault system in northern Chile. The magnetotelluric and geomagnetic response functions in the frequency range from 1000 Hz to 0.1 Hz clearly image a fault zone conductor (FZC) about 350 m wide and 1500 m deep, trending along the surface trace of the fault. The position of the FZC and its geometric properties (width, dip) correlate with a region of intense fluid alteration and the orientation of fault-related damage elements (minor faults, fractures). According to estimates of fluid salinity and rock porosity, the conductivity anomaly results from meteoric water penetrating into a permeable zone. This suggests that the increase in electrical conductivity is causally related to a mesh of minor faults and fractures, acting as a pathway for fluids. The FZC reflects the central and most fractured part of the damage zone. In view of similar published magnetotelluric studies, we infer a dependency of a fault's state of activity and the characteristics of the FZC such as its conductance, width, and depth extent. Ongoing deformation is the controlling factor for maintaining a permeable and electrically conductive fracture network.

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Electrical conductivity images of active and fossil fault zones

Cited by 69 publications

References 85 publications

Crustal metamorphic fluid flux beneath the Dead Sea Basin: constraints from 2-D and 3-D magnetotelluric modelling

Crustal metamorphic fluid flux beneath the Dead Sea Basin: constraints from 2-D and 3-D magnetotelluric modelling

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

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