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Structure and geometry of the Aksay restraining double bend along the Altyn Tagh Fault, northern Tibet, imaged using magnetotelluric method
Author(s) -
Xiao Qibin,
Yu Guo,
LiuZeng Jing,
Oskin Michael E.,
Shao Guihang
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl072581
Subject(s) - geology , magnetotellurics , seismology , classification of discontinuities , electrical resistivity and conductivity , tectonics , slip (aerodynamics) , fault (geology) , shear (geology) , geometry , active fault , strike slip tectonics , petrology , mathematical analysis , physics , mathematics , engineering , electrical engineering , thermodynamics
Large restraining bends along active strike‐slip faults locally enhance the accumulation of clamping tectonic normal stresses that may limit the size of major earthquakes. In such settings, uncertain fault geometry at depth limits understanding of how effectively a bend arrests earthquake ruptures. Here we demonstrate fault imaging within a major restraining bend along the Altyn Tagh Fault of western China using the magnetotelluric (MT) method. The new MT data were collected along two profiles across the Aksay restraining double bend, which is bounded by two subparallel strands of the Altyn Tagh Fault: Northern (NATF) and Southern (SATF). Both two‐dimensional (2‐D) and three‐dimensional (3‐D) inversion models show that the Aksay bend may be the center of a positive flower structure, imaged as a high‐resistivity body extending to an ~40 km depth and bounded by subvertical resistivity discontinuities corresponding to the NATF and SATF. In the western section of the Aksay bend, both the NATF and SATF show similar low‐resistivity structure, whereas in the eastern part of the bend, the low‐resistivity anomaly below the SATF is wider and more prominent than that below the NATF. This observation indicates that the SATF shear zone may be wider and host more fluid than the NATF, lending structural support to the contention that fault slip at depth is asymmetrically focused on the SATF, even though surface slip is focused on the NATF. A south dipping, low‐resistivity interface branching upward from the SATF toward the NATF indicates a fault link between these strands at depth.