科研之友
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摘要
The 1000-km-long Haiyuan fault system on the northeastern edge of the Tibetan Plateau contributes to accommodating the deformation in response to the India/Asia collision. In spite of its importance, the kinematics of the fault including the geometry and along-strike slip rate have not been completely defined. In this study, we use synthetic aperture radar data acquired between 2014 and 2021 by Sentinel 1 satellites to investigate the present-day strain accumulation on the Haiyuan fault system. We produce a high-resolution velocity map for the similar to 300,000 km(2) Haiyuan region using the Small BAseline Subset method. Our new velocity fields reveal deformation patterns dominated by the eastward motion of Tibet relative to Alaxan and localised strain accumulation along the Haiyuan, Gulang and XiangshanTianjingshan faults. The western similar to 300-km-long section of the Haiyuan fault, which was previously unmapped, seems to follow Tuolaishan and terminate at Halahu. We compute the along-strike slip rate using a Bayesian Markov Chain Monte Carlo inversion approach, and find that the overall strike-slip rate along the Haiyuan fault system gradually increases from the western end (1.8 +/- 0.3 mm/yr close to Halahu) to the east (6.4 +/- 0.5 mm/yr before entering Liupanshan), and further east, it decreases from 6.4 +/- 0.5 mm/yr to 1.3 +/- 0.7 mm/yr. The Haiyuan fault absorbs most of the left-lateral strike-slip motion with a rate of -4.2 +/- 0.4 mm/yr, and the Gulang and Xiangshan-Tianjingshan faults take up a fraction of 2.2 +/- 0.6 mm/yr. We re-map the previously identified shallow creeping zone on the Laohushan segment for a length of 45 km, slightly larger than the previous estimate of 35 km. The average shallow creep rate, 3 mm/yr between 2014-2021, is consistent with the rate before 2007 (2-3 mm/yr), implying that the shallow creep is a steady behaviour.
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