焉耆盆地活动断层的晚第四纪右行走滑
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摘要
本研究对天山东南侧山间盆地——焉耆盆地的晚第四纪右行走滑活动断层的位移和滑动速率进行了测量.详细的卫星图像分析和野外调查表明活动断层(开都河断层带)主要分布在盆地的南缘,具典型的走滑断层特征.发育在晚更新世—全新世冲积扇中的水系记录了3～250 m的右行错断和位移的累积.冲积扇中的断层陡坎高1 m到25 m,沿断层带走向左行雁列状断层崖呈现,向NE和SW倾.基于河道的错断,14C数据和断层岩组构的分析可以得出:①活动断层的平均右行走滑速率为8 mm/a,垂直分量的速率为1 mm/a,(②典型的单次地震断裂事件产生的错断量为3～7 m,③大地震事件(Ms>7)的平均重复间隔约为500年,④开都河断层带最新的地震断裂事件发生在过去2 500 a间.与印度—欧亚板块碰撞相关联的天山是一个逆冲构造占主导地位的造山带,而山间盆地中晚第四纪的走滑断层表明了这种造山机制中具有水平滑动.
Late Quaternary right-lateral displacement and slip rates have been determined along WNW-ESE trending active faults in the intermontane Yanqi basin on the southeastern flank of the Chinese Tian Shan. Detailed analyses of satellite images and field investigation have revealed that the active Kaidu River fault zone on the southern margin of the basin is a strike-slip fault zone. Drainage systems incising late Pleistocene-Holocene alluvial fans record between 3 m and 250 m dextral offsets and show progressive displacement along the fault zone. Fault scarps developed in the alluvial fans range in height from 1 m to 25 m and alternate along the strike of the fault zone from northeast-facing to southwest-facing in a left-stepping en-echelon pattern. Based on the offset of stream channels, 14C dates of alluvial deposits, and fabrics within fault rocks, we infer that ㏕he average right-lateral slip rate is about 8 mm/year, with a vertical component of 1 mm/year, the offset produced by individual seismic faulting event is typically 3-7 m, the average recurrence interval of large seismic events (Ms>7) is ca. 500 years, and the most recent movement occurred during the past 2.5 ka in the Kaidu River fault zone. These strike-slip faults represent partitioning of horizontal slip within an otherwise thrust dominated orogen related to the India-Eurasia collision within the Tian Shan during late Quaternary.
Late Quaternary right-lateral displacement and slip rates have been determined along WNW-ESE trending active faults in the intermontane Yanqi basin on the southeastern flank of the Chinese Tian Shan. Detailed analyses of satellite images and field investigation have revealed that the active Kaidu River fault zone on the southern margin of the basin is a strike-slip fault zone. Drainage systems incising late Pleistocene-Holocene alluvial fans record between 3 m and 250 m dextral offsets and show progressive displacement along the fault zone. Fault scarps developed in the alluvial fans range in height from 1 m to 25 m and alternate along the strike of the fault zone from northeast-facing to southwest-facing in a left-stepping en-echelon pattern. Based on the offset of stream channels, 14C dates of alluvial deposits, and fabrics within fault rocks, we infer that ㏕he average right-lateral slip rate is about 8 mm/year, with a vertical component of 1 mm/year, the offset produced by individual seismic faulting event is typically 3-7 m, the average recurrence interval of large seismic events (Ms>7) is ca. 500 years, and the most recent movement occurred during the past 2.5 ka in the Kaidu River fault zone. These strike-slip faults represent partitioning of horizontal slip within an otherwise thrust dominated orogen related to the India-Eurasia collision within the Tian Shan during late Quaternary.
引文
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[2] Seismological Bureau Xinjiang Uygur Autonomous Region(SBXUAR),1/2,000,000 Seismotectonic map Xinjiang UygurAutonomous Region, China[M], 1997．
[3] Molnar P, Brown E T, Burchfiel B C, et al. Quaternary climate changeand the formation of river terraces across growing anticlines on thenorth flank of the Tien Shan, China[J]. J. Geol, 1994, 102: 583-602．
[4] Tapponnier P, Molnar P. Active faulting and Cenozoic tectonics of theTien Shan, Mogolia and Baykal Regions[J]. J. Geophys. Res, 1979, 84:3425-3459．
[5] Windley B F, Allen M B, Zhang C, et al. Paleozoic accretion andCenozoic redeformation of the Chinese Tien Shan Range, centralAsia[J]. Geology, 1990,18:128-131．
[6] Allen M B, Windley B F, Zhang C. Active alluvial system in the KorlaBasin, Tien Shan, northwest China: Sedimentation in a complexforeland basin[J]. Geol Mag, 1991,128:661-666．
[7] Avouac J P, Tapponnier P, Bai M, et al. Active thrusting and foldingalong the northern Tien Shan and late Cenozoic rotation of the Tarimrelative to Dzungaria and Kazakhstan[J]. J. Geophys. Res, 1993, 98:6755-6804．
[8] Deng Q, Zhang P, Xu X, et al. Paleoseismology of the northernpiedmont of TIanshan Mountains, northwestern China[J]. J. Geophys.Res., 1996,101:5895-5920．
[9] Brown E T, Bourle s D L, Burchfiel B C, et al. Estimation of slip ratesin the southern Tien Shan using cosmic ray exposure dates ofabandoned alluvial fans[J]. Geol. Soc. Am. Bull, 1998,110:377-386．
[10] Allen M B, Windley B F, Zhang C. Cenozoic tectonics in theUrnmqi-Korla region[J]. Geol. Rundsch, 1994,83:406-416．
[11] Chen H. Explanation of Quaternary geological map (1:1,500,000) of Xinjiang Uygur Autonomous Region, China[M]. Geological Publishing House, Beijing, 1994,132．
[12] 新疆地质矿产局,新疆维吾尔自治区区域地质志[M].北京:地质出版社,1993．
[13] Research Group for Active Faults of Japan (RGAF Japan), Active Faults in Japan: Sheet Maps and Inventories (in Japanese with English abstract)[M]. Tokyo: The University of Tokyo Press, 1980．
[14] Research Group for Active Faults of Japan (RGAF Japan), Active Faults in Japan: Sheet Maps and Inventories (Revised Edition, in Japanese with English abstract)[M]. Tokyo: The University of Tokyo Press, 1991．
[15] Lin A, Maruyama T, Miyata T. Paleoseismic events and the 1596 Keicho-Fushimi large earthquake in the Gosukebashi fault in the eastern Rokko Mountains[J]. The Island Arc, 1998, 7: 621-636．
[16] 冯先岳.新疆古地震[M].乌鲁木齐:新疆科技卫生出版社(K),1997．
[17] Fu B, Lin A, Kano K, et al. Application of satellite remote sensingimagery for studying active tectonic structures in the southern TianShan, northwest China[J]. International Remote Sensing, submitted,2001．
[18] Lin A. Microstructures of the fault rocks in the Nojima fault and theirimplications for the tectonic history[J]. Structural Geology, The Jour.Structural Research Group of Japan, 1996,41: 17-29 (in Japanese withEnglish abstract).
[19] Lin A, Shimamoto T, Maruyama T, et al. Comparative study of thecataclastic fault rocks found in cores and outcrops along the Nojimafault in Awaji Island, Japan[J]. The Island Arc, 2001,10: 368-380．
[20] Kano K, Lin A, Maruyama T. Late Quaternary activity of theSakai-toge fault zone[J]. Quaternary Research, in press (in Japanesewith English abstract), 2001．
[21] Maruyama T, Lin A. Late Quaternary faulting history of the strike-slipactive faults inferred from offsets of topographic features and basementrocks: a case study of the Arima-Takatsuki Tectonic Line, southwestJapan[J], Tectonophysics(in press),2001．
[22] Burchfiel B C, Royden L H. Tectonics of Asia 50 years after the deathof Emile Argand[J]. Eclogae Geol. Helv., 1991, 84: 599-629．
[23] Allen M B, Vincent S J, Wheeler P J. Late Cenozoic tectonics of theKepingtage thrust zone: Interactions of the Tien Shan and Tarim Basin,northwest China[J]. Tectonics, 1999,18: 639-654．
[24] Yin A, Nie S, Craig P,
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