Late Quaternary left‐lateral slip rate of the Haiyuan fault, northeastern margin of the Tibetan Plateau

Abstract

Slip rates of major active strike‐slip faults within and around the Tibetan Plateau provide constraints for understanding the dynamics of continental deformation in general because large slip rates can be taken to imply localized deformation between rigid blocks and low slip rates on faults are more consistent with distributed deformation. Several major strike‐slip faults have been studied during the last 3 decades. As one of important active strike‐slip faults in and around the Tibetan Plateau, the slip rate of the Haiyuan fault has been discrepantly estimated to be high by proponents of “escape tectonics” or low by others and GPS observations. To better constrain its slip rate and then to better understand the mechanics of intracontinental deformation, we try to more carefully consider offset geomorphic features and age constraints along the Haiyuan fault. In this paper, we select three sites where both upper and lower bounds of slip rate can be obtained. We find that slip rates are 4.2 ± 0.8 mm/yr at the Shaomayin, 4.5 ± 0.7 mm/yr at Gaowanzi, and 5.0 ± 2.5 mm/yr at Huangliangtan site. Combinations of these rates with those published previously yield an average slip rate of 4.5 ± 1.0 mm/yr on the Haiyuan fault. This rate agrees with the present‐day slip rate of 4.3 ± 1.5 mm/yr measured by GPS, 4.2–8 mm/yr by interferometric synthetic aperture radar, and ∼5 mm/yr through paleoseismological studies. The temporal consistency suggests a steady state process of strain accumulation and release along the Haiyuan fault. The low slip rate suggests that the Haiyuan fault, similar to the Altyn Tagh fault, does not transfer a significant portion of the convergence between India and Asia out of India's path into Eurasia but merely redistributes crustal thickening.