野马河—大雪山断裂肃北段晚第四纪活动特征研究

Investigation of Late Quaternary Activity along Subei Fault

前人对野马河—大雪山断裂肃北段的晚第四纪活动特征研究相对薄弱,缺少有关断层最新活动的证据。本文在高分辨率遥感解译的基础上,对肃北断裂开展全段1∶5 000的地质地貌填图,通过探槽开挖、放射性碳(^(14)C)测年以及低空无人机摄影测量(small Unmanned Aerial Vehicles,简称sUAV)等工作,对该断裂晚第四纪活动性进行系统研究。发现肃北断裂为一条全新世的逆冲活动断裂,晚第四纪以来具有多期活动,西水沟探槽剖面揭示出2次古地震事件,古地震离逝时间为(4 192.5±97.5)a B.P.之后。

The Subei Fault is located in the western part of the Yema River-Daxue Mountain fault, which is located in the northeast of the Tibetan Plateau. This fracture is about 17 km long, trends north- west 40°, and crosses the Altyn Tagh Fault in the Subei area. The conventional view is that the power of the Altyn Tagh Fault with a high slip rate （about 10 ram/a） was absorbed by the Tanghe Nan Shan fault, the Yema River-Daxue Mountain fault, the Changma fault, and so on. Some of this power was also tranversed to form a thrust fault, after which the slip rate of the Altyn Tagh Fault decreased to 1 2 mm/a. There has been little formal research and no systematic study made of the late Quaternary ac- tivity along the Subei Fault. Using high-resolution satellite imagery and systematically studying the Subei late Quaternary, based on the structure transform mode put forward by Xu Xiwei in 2003. Moreover, our study shows the sUAV to have broad application prospects. We can rebuild a digital elevation mode based on hundreds of pictures collected by sUAVs with a very high precision. Using this technology, we can also build digital orthoimages any places we wish. Using digital elevation models （DEMs）, we chose typical landforms and extracted their profiles to show the altitude of the scarps. We compared the alti- tudes measured by the DEM profile with measurements by the laser range finder, and found the meas- urement results to be basically the same. Combining several fault profiles along the Subei Fault and that of a trench excavated in Xishuigou, we determined that the Subei Fault is mainly a thrust fault, with lin- ear and continuous scarps along the fault.