GEOMORPHIC FEATURES AND REMOTE SENSING RESEARCH OF FAULT ACTIVITY ALONG THE SOUTHEASTERN PIEDMONT FAULTS OF NYENCHEN TONGLHA MOUNTAINS

doi:10.3969/j.issn.0253-4967.2015.02.022

Abstract

Abstract:

Based on ALOS, ETM+images and field works, combining with the existing research results of the study area, using information enhancement and image fusion methods, we extracted the texture, color and water-bearing features and studied the spatial distribution and development of the southeastern piedmont faults of the Nyenchen Tonglha Mountains. Moreover, SL index and Hack profile were used to analyze and compare the regional tectonic activity. The results show that the main faults obviously present a three-stage distribution on remote sensing images. Fault movement has produced different surface topography, such as fault scarp, fault facet and surface rupture zone. Small pull-apart basin, rift lakes and swamps were found in the basin. Their distribution and development are obviously controlled by faults. Geomorphic evidences interpreted from images generally indicate the fault movement property as normal faulting with strike-slip component. Major rivers cross the southeastern piedmont faults of the Nyenchen Tonglha Mountains from northwest to southeast and flow into Dangxiong-Yangbajain rift basins. The rivers with length bigger than four kilometers are selected to calculate the tectonic geomorphology parameters. The Hack profiles of rivers present obvious convex uplift that represents strong tectonic differential uplifting. Rivers had no time to make adjustments in the process of development and the tectonic movement produced convex and concave shape on the river section traces. The area where standard stream length-gradient index is abnormal indicates strong tectonic movement. This abnormal changes not only verify the impact on river profile caused by fault movement, but also improve the fault location accuracy when interpreted combining with these abnormal features. The average SL/K value in this area tends to increase from F₁ to F₃. From the point of historical earthquakes distribution, a large amount of small earthquakes occurred mainly on F₃ and seldom on F₁ and F₂. This trend is similar to SL/K value change. It indicates that the fault activity increases accordingly from F₁ to F₃. The standard length-gradient index K represents the river erosion ability, which increases from F₁ to F₃. This feature shows that normal fault movement is strong on F₃ and tectonic uplift has a significant impact on river erosion. Movement on F₁ and F₂ show strong strike-slip and weak normal faulting, whereas normal faulting is stronger on F₃. Dislocation of rivers is more evident on the remote sensing image. The southeastern piedmont faults of Nyenchen Tonglha Mountains and Dangxiong-Yangbajain rift basins are important conversion and absorption zones in the central Tibetan plateau, where the seismic activity is still high and more attention should be paid.

Key words: southeastern piedmont faults of Nyenchen Tonglha Mountains, stream length-gradient index, Hack profile, remote sensing interpretation

摘要：

选用高分辨率ALOS和中等分辨率ETM+图像, 结合研究区已有研究成果, 采用信息增强及图像融合方法, 对图像中各类构造地貌表现出的纹理、色调及含水性特征进行研究, 建立了解译标志, 并结合野外调查结果, 系统解译了念青唐古拉山东南麓断裂带的展布与发育情况; 同时引入河长坡降指标参数(SL index)和Hack剖面(河流高程剖面半对数坐标图)2个构造地貌参数, 分析其对区域构造活动的指示意义并比较断裂带不同分段的活动性。研究表明, 念青唐古拉山东南麓断裂带呈三段式展布, 遥感解译的地貌标志基本反映了断裂带以正断层为主兼具走滑运动性质。呈明显的上凸形态的河流Hack剖面反映了区内构造差异隆升强烈, 河长标准化坡降指标明显异常地带指示为构造运动活跃区, 这种异常变化不仅印证了断层活动对河床剖面的影响, 而且结合该变化特征进行遥感解译可以提高断裂位置解译的准确性。断裂的活动性从F₁向F₃依次增强, F₁、F₂段正断层活动性相对较弱, 走滑活动增强, F₃段正断层活动性较强。

关键词: 念青唐古拉山东南麓断裂带, 河长坡降指标, Hack剖面, 遥感解译

CLC Number:

P315.2

JIAO Qi-song, ZHANG Jing-fa, JIANG Wen-liang. GEOMORPHIC FEATURES AND REMOTE SENSING RESEARCH OF FAULT ACTIVITY ALONG THE SOUTHEASTERN PIEDMONT FAULTS OF NYENCHEN TONGLHA MOUNTAINS[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(2): 613-626.

焦其松, 张景发, 姜文亮. 念青唐古拉山东南麓断裂带构造地貌特征与活动性遥感研究[J]. 地震地质, 2015, 37(2): 613-626.

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