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- Title
Late Quaternary Slip Rate of the Zihong Shan Branch and Its Implications for Strain Partitioning Along the Haiyuan Fault, Northeastern Tibetan Plateau.
- Authors
Yao, Wenqian; Liu‐Zeng, Jing; Klinger, Yann; Wang, Zijun; Shao, Yanxiu; Han, Longfei; Wang, Wei; Zhang, Jinyu; Liu, Zhijun
- Abstract
Geometrical complexities such as bends and branches are ubiquitous along strike‐slip faults. Understanding strain partitioning between the different fault strands along such sections is key to assessing kinematics and evolution through time of a fault system and related seismic hazards. The Haiyuan fault, one of the longest strike‐slip faults of the Tibetan Plateau, has developed a multi‐stranded complex fault geometry along the Hasi Shan restraining bend. In this study, we quantified the slip rate of the ∼50‐km‐long Zihong Shan fault, which is the poorly‐known southernmost fault strand of the Hasi Shan restraining bend. We computed high‐resolution DEMs and orthophotos to document the offset landforms along this fault using drone surveys. At selected sites with well‐preserved offset geomorphic markers, we quantified displaced terraces and channels using microtopography analysis. We dated the abandonment age of these terraces using 10Be cosmogenic depth profiles and OSL dating techniques. It yields a left‐lateral slip rate of 1.9 ± 0.6 mm/yr since ∼13 ka, which is similar to the rate of the main Hasi Shan branch that ruptured during the 1920 Haiyuan earthquake. The minimum total horizontal slip rate system summed over the multiple strands of the Haiyuan fault at the Hasi Shan restraining bend is 4.1 ± 0.6 mm/yr, without considering the vertical deformation rate of these fault strands. The rate is thus slightly smaller than, but comparable to, slip‐rates determined along the rest of the Haiyuan fault, east and west of the Hasi Shan restraining bend. Plain Language Summary: Quantifying the slip rate of each fault strand in an area with complex fault geometry is key to understanding how deformation is accommodated along different sections of a large strike‐slip fault. Here, studying the poorly‐documented left‐lateral strike‐slip Zihong Shan fault strand provides critical insight into strain partitioning between fault strands along the complex Haiyuan strike‐slip fault system. Combining our displacement measurements and geochronology data yields a geological slip rate of 1.9 ± 0.6 mm/yr since ∼13 ka along the Zihong Shan fault. The minimum total horizontal slip rate across the entire Hasi Shan restraining bend is thus 4.1 ± 0.6 mm/yr. This value is slightly less, although consistent than rates obtained farther east and west along the Haiyuan fault. However, the vertical deformation of different strands at the Hasi Shan restraining bend should not be overlooked and could make a difference. The seismic hazard along the Zihong Shan branch might be greatly underestimated. Key Points: The slip rate of the Zihong Shan fault is determined to be 1.9 ± 0.6 mm/yr over the last ∼13 kaThe minimum total horizontal slip rate across the Hasi Shan section is 4.1 ± 0.6 mm/yr, similar to other sections of the Haiyuan faultThe Zihong Shan fault itself could be the source of an earthquake of magnitude MW ∼7, or larger
- Subjects
DISPLACEMENT (Mechanics); EARTHQUAKE magnitude; STRIKE-slip faults (Geology); OPTICALLY stimulated luminescence dating; DEPTH profiling; PLATEAUS; TSUNAMI warning systems; KINEMATICS
- Publication
Journal of Geophysical Research. Solid Earth, 2022, Vol 127, Issue 5, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB023162