东天山博格达山前构造变形与地形定量关系:基于三维建模与地貌分析

Quantitative Relationship between Tectonic Deformation and Topography in Bogda Piedmont of Eastern Tianshan Mountains:Based on 3D Structural Modeling and Geomorphic Analysis

东天山受印度-欧亚板块碰撞的远程影响,新构造活跃,同时在气候影响下地表侵蚀速率有明显的空间差异,是探讨构造活动、地表过程和气候变化相互作用的理想区域;而反映构造变形的断层滑移量和地形起伏度是理解构造和气候相互作用的重要参数.通过三维地震反射深度剖面解译构建东天山阜康断裂带西端古牧地背斜三维构造几何形态,发现阜康断裂带断层倾角约为40°~50°,发育断层传播褶皱,且构造变形起始于断层中部(甘河子附近),逐渐向东西两侧传播.断层滑移量(Sl)与地形起伏度(△H)呈线性相关,基于两者的线性关系,计算获得阜康断裂带中部最大剥蚀量约5.05 km,最大缩短量约为9.20 km,剥蚀速率约为0.38~0.60 mm/a.阜康断裂带比北天山吐谷鲁背斜处的断层倾角更陡,但两处地形起伏度均为断层滑移量的~1/10,说明残余地形主要受控于造山楔构造和侵蚀的动态平衡作用.

The specific neotectonic activities,spatial variations of erosion rates in Tianshan Mountains are led by the far-field effect of the India-Asia collision and variable precipitations.It is an ideal place to discuss the interaction of tectonic,surface processes and climatic change.The relationship of the amount of fault slip and topographic relief in this area might provide clues for understanding the interaction between tectonic and climate,and resulted topography.In this study,the subsurface three-dimensional structural geometry model of a fault-related anticline(Gumudi)at the western fault zone(Fukang)at the eastern Tianshan Mountains was constructed by the interpretation of the 3 D seismic reflection data in depth.It shows that the dip of the fault is about 40°-50°,and fault-propagation folds developed.The tectonic deformation of this fault originated from the central zone and gradually propagated to the east and west ends.The amounts of the fault slip and the topographic relief at different areas were calculated from the subsurface three-dimensional tectonic structural geometry.The results show that the topographic relief(△H)is linearly related to the amount of fault slip(Sl).The maximum denudation,the maximum shortening,and the denudation rate are deduced to be as about 5.05 km,9.20 km,and 0.38-0.60 mm/a,respectively,in the central area of the Fukang fault zone,which is based on the linear relationship between the faultslipandthetopographic relief.In addition,it presents a similar relationship that△H was equal to 1/10 Slat different areas in spite of quite various dip angles of faults.This indicates that the relict topography is mainly controlled by the dynamic balance of the tectonic activities and erosion of the orogenic wedge rather than the magnitudes of the fault dip in this area.