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

Hoffmann‐Rothe, A.; Ritter, O.; Janssen, C.

doi:10.1029/2004jb003030

Cited by 38 publications

(19 citation statements)

References 62 publications

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“…Becken et al (2008) imaged the deep resistivity structure (surface-25 km) near the San Andreas Fault Observatory at Depth (SAFOD) and also pointed out the presence of FZC. MT images for the West Fault in northern Chile confirmed earlier studies and showed FZCs (Hoffmann-Rothe et al, 2004).…”

Section: Discussionsupporting

confidence: 76%

“…Both Ritter et al (2005) and Hoffmann-Rothe et al (2004) presented tables for comparing FZC properties of various faults. These properties include the activeness of the fault segment, and the width and depth of the FZC, as well as the lateral conductance (lateral conductance = the width of the conductor × average conductivity), observed in relation to the FZC (see the discussion in Ritter et al (2005) on lateral conductivity; page 170).…”

Section: Comparison Between Fzcs On Other Faultsmentioning

confidence: 99%

“…Some important instances of these studies are as follows. Hoffmann-Rothe et al (2004) investigated the West Fault (WF) in northern Chile. Ritter et al (2003) studied the Avara Fault (AvF) on the Dead Sea Transform in Jordan where they found an impermeable barrier for uid ow.…”

Section: Introductionmentioning

confidence: 99%

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Fault zone conductors in Northwest Turkey inferred from audio frequency magnetotellurics

Tank

2012

Earth Planet Sp

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A comparison of the electrical properties of the two main branches of the North Anatolian Fault is made based on audio-frequency magnetotelluric (AMT) surveys carried out along three typical pro les across the North Anatolian Fault Zone (NAFZ). These two branches are (i) the active northern branch (Izmit-Adapazar Fault (IAF)) where the 17 August, 1999, Izmit earthquake took place, and (ii) the less active southern branch (IznikMekece Fault (IMF)). In this paper, we focus on the shallow depths (surface-1.5 km) in search for conductors near the fault zone for the purpose of comparing these two branches with each other, as well as other strike-slip faults. Phase tensor analyses and Groom-Bailey decompositions were applied to check the dimensionality of the AMT data. Following the tensor analyses and decompositions, two-dimensional inversions were carried out to yield models based on the transverse electric (TE), and transverse magnetic (TM), modes. These models suggest that the North Anatolian Fault exhibits signs of fault zone conductors (FZC) regardless of being active or less active.

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Section: Discussionsupporting

confidence: 76%

Section: Comparison Between Fzcs On Other Faultsmentioning

confidence: 99%

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Fault zone conductors in Northwest Turkey inferred from audio frequency magnetotellurics

Tank

2012

Earth Planet Sp

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“…Elevated conductivities surrounding the uppermost portion of the fault were also imaged at Carrizo plain, though as a less pronounced feature of the resistivity model ( Figure 5a). Such a fault-zone conductor (FZC), prominently apparent at Parkfield and Hollister, and modest at Carrizo Plain, is believed to correspond to saline fluid circulation within the damage zone of the fault and appears to be typical for the SAF and for many other faults worldwide (Ritter et al 2005;Hoffmann-Rothe et al 2004).…”

Section: The Fault Zone Conductormentioning

confidence: 99%

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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Fluids residing in interconnected porosity networks have a significant weakening effect on rheology of rocks and can strongly influence deformation along fault zones. The magnetotelluric (MT) technqiue is sensitive to interconnected fluid networks, and can image these zones on crustal and upper mantle scales. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, fault creep is supported. In response to fluid flux from deeper levels in combination with meteoric and crustal metamorphic fluid supply, and in response to fault creep, high-conductivity zones develop as fault zone conductors in the brittle portion of crust. In turn, the absence of crustal fluid pathays may be characteristic for mechanically locked segments. MT models suggest that those fluids are trapped at depth and kept at high pressures. It is speculated that fluids may infiltrate neighbouring rocks and induce non-volcanic tremor. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, strain provides a means to develop and maintain permeability structure, and thus electrical conductivity, within the damage zone. Accordingly, these conductivity models played an important role in pin-pointing the SAFOD drilling location near Parkfield. *abstractClick here to download abstract: abstract.txt Surv. Geophys. manuscript No.In this paper, we consider MT studies at the SAF near Hollister and Carrizo The SAF has also been a target for telluric (Madden et al. 1993;Park et al. 2007) and magnetotelluric monitoring (e.g. Kappler et al. 2010). These installations attempted to monitor long-term electric (and magnetic) field variations of internal origin due to resistivity variations assiciated with earthquakes, large scale fluid flow or other causes. To date, it was not possible to identify significant field variations which can be attributed to tectonic processes. In this paper, we don't discuss details of this issue. 7The main objective of this paper is to review the MT results from the SAF in combination with other geophysical, geological and geochemical data and models in order to address fluid-related processes and their potential implications on the geodynamic setting, active tectonic processes and the mechanical ...

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“…Thus, low resistivity zones at subsolidus temperatures are often interpreted as porous zones with fluid. For example, the observed low resistivity images along the faults could be explained as the existence of an abundant quantity of fluid in cracks or fault breccias (e.g., Unsworth et al, 1997;Hoffmann-Rothe et al, 2004). Recent magnetotelluric (MT) investigations have also revealed low resistivity zones distributed in the mid to lower crust beneath the intraplate earthquake zones (e.g., Mitsuhata et al, 2001;Ogawa et al, 2001;Ogawa and Honkura, 2004;Wannamaker et al, 2004;Uyeshima et al, 2005;Yoshimura et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Resistivity structure around the focal area of the 2004 Rumoi-Nanbu earthquake (M 6.1), northern Hokkaido, Japan

et al. 2008

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The Rumoi-Nanbu earthquake (M 6.1) occurred in northern Hokkaido, Japan, on December 14, 2004. We conducted MT surveys along three profiles in and around the focal area to delineate and decipher the structural features of the seismogenic zone. The inverted 2-D resistivity images of the three sections comprised two layers: an upper conductive layer and a lower resistive layer. The boundary of these layers lay at a depth of approximately 3-5 km. A comparison with the surface geology and drilling data revealed that the upper conductive layer and the lower resistive layer corresponded to the Cretaceous-Tertiary sedimentary rocks and older basement rocks, respectively. A clear upheaval of the layer boundary was found along the profile at the center of the focal area. In addition, borehole data indicated an obvious increase in the Young's modulus toward the lower layer. Therefore, the elastic properties with a complex geometry around the focal zone tended to vary; this probably depicts the zone of stress accumulation that triggered the earthquake.

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

Cited by 38 publications

References 62 publications

Fault zone conductors in Northwest Turkey inferred from audio frequency magnetotellurics

Fault zone conductors in Northwest Turkey inferred from audio frequency magnetotellurics

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Resistivity structure around the focal area of the 2004 Rumoi-Nanbu earthquake (M 6.1), northern Hokkaido, Japan

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