Late Quaternary Slip Rate of the Aksay Segment and its fast decreasing gradient along the Altyn Tagh Fault
Abstract
The Altyn Tagh Fault (ATF) is an important large strike-slip fault in the northeastern Tibetan Plateau. Along with the uplift of the NW mountains in the south of the Qilianshan, the eastern segment of ATF becomes a very important tectonic transformation area. Accurate determination of the slip rate in time and space is helpful to reveal the tectonic deformation process of the northeastern Tibetan Plateau and the tectonic transition relationship among different blocks.
For large-scale displacement restoration, image data can be used, combined with geomorphic evolution analysis to obtain reasonable displacement. For the small-scale displacement, we use High-resolution DEM to measure displacements, which is obtained by the photogrammetry technique. The acquisition of the ages of the deformed landforms mainly depends on optically stimulated luminescence (OSL) and in situ cosmogenic nuclides (10Be) dating methods. When calculating the slip rate of four research sites, we use the displacement-age sequence of multiple offset terraces in the Aksay old county and the Jiaerwuzongcun. Monte Carlo simulation method is used to analyze the error of displacement-time synthetically. The slip rate of the west of the Aksay old county is 10.9±1.2 mm/yr since 9 ka. At Aksay old county, the slip rate is 10.2+1.2/-1.1 mm/yr since 220 ka, consistent to the previous results of the slip rate since 7 ka. These results indicate that the slip rate of the ATF is stable at different time scales at Aksay segment. The slip rates of the Jiaerwuzongcun and Yandantu is 7.5+1.2/-0.6mm/yr since 7ka and 5.1±0.8mm/yr since 7ka. By analyzing the spatial variation of the slip rate in east segment of the ATF, the slip rate reduction has occurred in the middle position of the Aksay segment, from the 9~11mm/yr in the Akasy old county to 7.5+1.2/-0.6mm/yr in the Jiaerwuzongcun, which decreased about 50% to be 5.1±0.8mm/yr near the Yandantu. According to the results of previous study, we analyse the spatial distribution of slip rate in the whole ATF east segment and suggests that the slip rate of the east section of the ATF decreases faster in the Aksay-Subei segment, from the 9~11mm/yr to 5.1±0.8mm/yr, which takes up the ~50% of the slip rate within ~50 km with slip gradient of 9.8mm/100 km. But the slip rate decreases slowly from the Subei to the east, the other 50% of the slip rate decreased to almost zero in 200 km distance with much lower gradient of 2.5 mm/100 km. The slip rate gradient at Aksay segment is ~4 times of that of Subei to the eastward termination of the Altyn Tagh fault. According to the results of the shortening rate of the middle section of the northern edge of Danghe Nan Shan, the shortening rate of the parallel ATF direction is only 0.8~1.0mm/yr. Hence, we proposed that the remained 3.9~4.1mm/yr is absorbed mainly by the uplift of the Danghe Nan Shan and the crustal shortening of the Cenozoic basins. This could also be the reason why the slip rate of the Altyn Tagh fault decreased fast at the Aksay segment. Our results indicate that the slip rate decreasing along the Altyn Tagh fault is not uniform at its termination segment, the gradient could be also variable.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T51B..03L
- Keywords:
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- 8036 Paleoseismology;
- STRUCTURAL GEOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8123 Dynamics: seismotectonics;
- TECTONOPHYSICS;
- 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS