We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Crustal Electrical Anisotropic Structure of the Altyn Tagh Fault in the Subei Area, NW China: Implications for Fault Zone Architecture.
- Authors
Dong, Zeyi; Xiao, Qibin; Sun, Zelin; Han, Bing; Wang, Lifeng; Tang, Ji; Wang, Jijun
- Abstract
The fault zone architecture may provide reliable information about the deformations in both on‐fault and off‐fault media. The outer damage zones of faults may extend for kilometers and exhibit structural anisotropy, which potentially causes electrical anisotropy in rocks. Thus, electrically anisotropic structures may indicate the dimensions and extent of fault damage zones. We investigated the electrical anisotropic structure of the sinistral Altyn Tagh fault (ATF), NW China, using magnetotelluric data collected in and around the Subei Basin. Our three‐dimensional resistivity model reveals widespread anisotropic anomalies at depths <∼5 km. The directions of the minimum horizontal resistivity values of the anomalies inside the Qilian Shan southeast of the ATF are dominantly subparallel to the fault traces at the surface. At deeper levels (∼15–19 km and ∼33–43 km), the anisotropic anomalies are mainly concentrated near the northern strand of the ATF (NATF) and the North Yemahe fault (NYMF) in the northeastern Subei area. The mid‐lower crust (∼33–43 km) inside the Qilian Shan is characterized by isotropy or weak anisotropy with low resistivities (∼10 Ωm), which deviate significantly from the values along the NATF. Our results indicate the presence of a ∼30 km wide off‐fault damage zone along the NATF and NYMF in the shallow crust that thins downward to the lower crust. We propose that the distribution of anisotropic anomalies is influenced primarily by neighboring faults. An independent deformation model could be appropriate for evaluating the relationships between the ATF and thrust faults within the Qilian Shan. Plain Language Summary: Damage zones of faults include the volumes of subsidiary structures that may occur in preferred orientations and induce electrical anisotropy. An electrically anisotropic structure, indicating direction‐dependent conductivity (the reciprocal of resistivity), may provide a new means to delineate the architecture of a fault, especially its damage zones. The sinistral Altyn Tagh fault (ATF) defines the northern boundary of the Tibetan Plateau. The architecture of the ATF has seldom been discussed from a three‐dimensional (3‐D) perspective. We obtained the 3‐D crustal electrical anisotropic structure in the area through which the ATF passes and found that widespread electrical anisotropic anomalies exist in the upper crust. As depth increases, the anisotropic anomalies become more concentrated below the northern strand of the ATF (NATF) and a parallel fault ∼15 km south of it. These features may imply the existence of a damage zone between the NATF and its parallel fault that is ∼30 km wide at a depth of ∼5 km and thins to ∼10 km in the lower crust. Our study suggests that the ATF and the thrust faults within the Qilian Shan may be more compatible with an independent deformation pattern. Key Points: Dense magnetotelluric data are inverted to examine the architecture of the Altyn Tagh fault in the Subei areaThe electrical anisotropic anomalies in the Subei area are likely controlled by faultsAnisotropic anomalies in the crust are interpreted to reflect off‐fault damage zones
- Subjects
ANISOTROPY; THRUST; ACQUISITION of data
- Publication
Journal of Geophysical Research. Solid Earth, 2024, Vol 129, Issue 7, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB028550