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  Electrical conductivity images of active and fossil fault zones

Ritter, O., Hoffmann-Rothe, A., Bedrosian, P. A., Weckmann, U., Haak, V. (2005): Electrical conductivity images of active and fossil fault zones. - In: High Strain Zones: Structure and Physical Properties, (Geological Society special publication ; 245), The Geological Society, 165-186.

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Ritter, Oliver1, 2, Author              
Hoffmann-Rothe, A.2, 3, Author
Bedrosian, P. A.2, 3, Author
Weckmann, Ute1, 2, Author              
Haak, V.2, 3, Author
3.1 Lithosphere Dynamics, 3.0 Geodynamics and Geomaterials, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, Author              
2.3 Earth's Magnetic Field, 2.0 Physics of the Earth, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, Author              
12.2 Geophysical Deep Sounding, 2.0 Physics of the Earth, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, ou_66027              
2Publikationen aller GIPP-unterstützten Projekte, Deutsches GeoForschungsZentrum, Potsdam, ou_44021              
3External Organizations, ou_persistent22              


Free keywords: -
 DDC: 550 - Earth sciences
 Abstract: We compare recent magnetotelluric investigations of four large fault systems: (i) the actively deforming, ocean-continent interplate San Andreas Fault (SAF), (ii) the actively deforming, continent-continent interplate Dead Sea Transform (DST), (iii) the currently inactive, trench-linked intraplate West Fault (WF) in northern Chile, and (iv) the Waterberg Fault/Omaruru Lineament (WF/OL) in Namibia, a fossilized intraplate shear zone formed during early Proterozoic continental collision. These fault zones show both similarities and marked differences in their electrical subsurface structure. The central segment of the SAF is characterized by a zone of high conductivity extending to several kilometres depth and attributed to fluids within a highly fractured damage zone. The WF exhibits a less pronounced but similar fault zone conductor (FZC) which can be explained by meteoric waters entering the fault zone. The DST appears different as it shows a distinct lack of a FZC and seems to act primarily as an impermeable barrier to cross-fault fluid transport. Differences in the electrical structure of these faults within the upper crust may be linked to the degree of deformation localization within the fault zone. At the DST, with no observable fault zone conductor, strain may have been localized for a considerable time span along a narrow, meter-scale damage zone with a sustained strength difference between the shear plane and the surrounding host rock. In the case of the SAF, a positive correlation of conductance and fault activity is observed, with more active fault segments associated with wider, deeper, and more conductive fault zone anomalies. Fault zone conductors, however, do not uniquely identify specific architectural or hydrological units of a fault. A more comprehensive whole-fault picture for the brittle crust can be developed in combination with seismicity and structural information. Giving a window into lower-crustal shear zones, the fossil WF/OL in Namibia is imaged as a sub vertical, 14 km deep, 10 km wide zone of high and anisotropic conductivity. The present level of exhumation suggests that the WF/OL penetrated the entire crust as a relatively narrow shear zone. Contrary to the fluid driven conductivity anomalies of active faults, the anomaly here is attributed to graphitic enrichment along former shear planes. Once created, graphite is stable over very long time spans and thus fault/shear zones may remain conductive long after activity ceases.


 Dates: 2005
 Publication Status: Finally published
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: eDoc: 7549
GFZPOF: 2.0 Geodynamik, Stoffkreisläufe und Ressourcen
DOI: 10.1144/GSL.SP.2005.245.01.08
 Degree: -



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Source 1

Title: High Strain Zones: Structure and Physical Properties
Source Genre: Book
Publ. Info: The Geological Society
Pages: - Volume / Issue: - Sequence Number: - Start / End Page: 165 - 186 Identifier: -

Source 2

Title: Geological Society special publication
Source Genre: Series
Publ. Info: -
Pages: - Volume / Issue: 245 Sequence Number: - Start / End Page: 165 - 186 Identifier: -