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对天山内部大型断裂带晚第四纪以来变形特征的研究是认知天山现今构造变形特征的重要途径。在大比例尺遥感影像解译的基础上,利用野外调查测量、探槽开挖及热释光测年的方法,对那拉提断裂进行了研究。那拉提断裂是一条晚第四纪以来仍有较强活动的大型逆冲左旋走滑断裂带,断裂带宽度巨大,由多条倾向不同的次级断裂组成,分布在南北宽数公里的范围内,这些滑动面是逆冲走滑断裂在地表分散形成的“正花状”构造。晚第四纪期间,那拉提断裂曾多次发生过断错地表的强震事件,是天山内部一条重要的地震构造带。断裂断错了那拉提山前晚第四纪以来的各级地貌面,主要表现为断层陡坎、冲沟水系和地貌面的左旋位移,根据实测陡坎高度和对应地貌面的定年,获得断裂所造成的南北向地壳缩短速率在O.8~1.1mm/a左右,表明天山内部同样存在明显的构造变形。结合目前已有的地震地质研究资料,对天山山前和天山内部吸收的变形量分配进行了讨论,认为天山南北两侧山前对变形量的吸收调节作用并不显著高于天山内部。那拉提断裂具有左旋走滑特征的发现,对于理解天山现今变形方式以及应变分配具有重要的意义。
The study of the deformation characteristics of the large-scale fault zone in the Tianshan since the late Quaternary is an important way to recognize the present-day structural deformation in the Tianshan Mountains. Based on the interpretation of large-scale remote sensing images, the Nalati fracture was studied by field surveying, trench excavation and thermoluminescence dating. The Nalati fault is a large thrust left-lateral strike-slip fault zone still relatively active since the late Quaternary. The fault zone is huge in width and consists of several sub-faults with different tendencies and is distributed in a range of kilometers north to south Within these slip surfaces are the “positive flower ” structures formed by the dispersal of thrust strike-slip faults on the surface. During the late Quaternary, the Nalati fault had many earthquakes on the fault surface and was an important seismic structural belt within the Tianshan Mountains. Faults ruptured the Nalati Mountain since the Quaternary last night, all levels of topography, mainly for the fault scarp, gutter and facies surface left-handed displacement, according to the measured height of the scarp and the corresponding geomorphological dating, obtained The crustal shortening rate caused by the fault is about O.8 ~ 1.1mm / a, indicating that there is also obvious structural deformation in the Tianshan Mountains. Based on the available seismological and geological data, the distribution of deformations absorbed in the Tianshan Piedmont and Tianshan Mountains is discussed. It is concluded that the deformation of the Tianshan Mountains before and after piedmont is not significantly higher than that of the Tianshan Mountains. The discovery that the Nalati fault has the features of left-lateral strike-slip is of great significance for the understanding of the present Tianshan deformation mode and strain distribution.