新疆阿尔泰山南部富蕴右旋走滑断裂带晚第四纪错断水系的遥感分析研究

富蕴断裂带位于阿尔泰山南侧,横切阿尔泰山褶皱带南缘及额尔齐斯深断裂,是一条呈北北西向展布的右旋走滑断裂带。沿断裂带发育一系列错断水系、错断冲积扇、挤压脊、走滑拉分盆地等反映右旋走滑活动的典型构造地貌标志。本研究在高分辨率遥感图像和数字高程模型分析的基础上,结合野外实地构造地貌测量,对沿富蕴断裂带发育的系统错断水系特征进行了详细分析研究。研究结果表明,沿富蕴断裂带发育不同级别的错断水系,大致可划分为6级:1931年地震形成的冲沟;90m左右断距的错断水系;150m左右断距的错断水系;500m左右断距的错断水系;1500m左右断距的错断水系;2000m以上断距的错断水系。同时,结合研究区及邻区的第四纪冰川资料讨论了不同级别水系可能形成时间:恰尔沟三级支流可能形成时间为末次冰期Ⅲ阶段末期,约20ka;恰尔沟二级支流可能形成时间为末次冰期Ⅰ阶段末期,约120ka;恰尔沟一级支流可能形成于该地区冰川广泛消融的倒数第2次冰期的Ⅱ阶段末期,约为250ka;恰尔沟、水磨沟、白杨沟、乌铁布拉克河、卡布尔特河等可能形成于倒数第3次冰期Ⅱ阶段末期,约为360ka。最后,我们估算出富蕴断裂带晚第四纪以来的平均右旋走滑速率为1.46～4.99mm/a。

LATE QUATERNARY SYSTEMATIC STREAM OFFSETS ALONG THE FUYUN RIGHT-LATERAL STRIKE-SLIP FAULT,ALTAY MOUNTAINS,CHINA

The Fuyun Fault Zone,a right-lateral strike-slip fault extending NNW,is located in the south of the Altay Mountains,Northeastern Xinjiang,China.Geomorphological features,such as offset streams,fluvial fans,terraces,pull-apart basins,and pressure ridges are well developed along the fault zone.These typical geomorphological features related to strike-slip fault are resulted from long term geomorphological growth,the dry and cold climate,as well as the little human activities in these mountain-regions.Our goal of this study is to document the Late Quaternary stream offsets along the Fuyun Fault Zone based on the analyses of high-resolution satellite images（Landsat TM,ASTER,ASTER DEM,and IKONOS data）as well as field observations.The result shows that offset streams along the Fuyun Fault Zone can be classified into six levels:8m,90m,150m,500m,1500m,and more than 2000m offsets.We inferred that these differently scaled stream offsets are likely formed in ca.1931A.D.,20ka,120ka,250ka,360ka,and Pliocene based on analyses of glacial data in the whole Altay Mountains.Finally,we estimate that a long-term slip rate is of 1.46～4.99mm/a since the Late Pleistocene（ca.360kaB.P.）,which is a little higher than the slip rate（1mm/a）of strike-slip faults in the Mongolian Altay Mountains and the one measured from the geodetic measurements（0.86～2.00mm/a）.But it is close to the result estimated from the geological data along the fault zone（4±2mm/a）.