滇西北程海-宾川断裂带第四纪分段活动性的构造地貌表现与限定

Tectonic Geomorphology Constrains on Quaternary Activity and Segmentation along Chenghai-Binchuan Fault Zone in Northwest Yunnan,China

青藏高原东南部边缘的程海-宾川断裂带是一条正断与左旋走滑运动兼具的复合型活动断裂,起着调节青藏高原内部物质向东挤出的重要作用,并控制着区域的主要强震活动.基于GIS(Geographic Information System)技术,利用遥感影像和DEM(Digital Elevation Model)数据提取该区的关键构造地貌信息,对其第四纪分段活动性及特征进行了分析探讨.结果表明,程海-宾川断裂带的第四纪活动具有明显的分段性及空间差异性.其北段的金官-程海盆地主边界断层以正断层活动性质为主,并具有整个断裂带上最高的垂直活动速率;中段的期纳断裂以左旋走滑运动为主,且具有最高的走滑活动速率;南段宾川盆地东缘边界断裂也以正断层活动为主,但垂直活动速率略低于北段.总体上看,程海-宾川断裂带第四纪期间的垂直活动性由北往南降低,水平走滑活动性由中段往南北两端降低.在活动强度方面,程海-宾川断裂带百万年尺度的长期活动速率一直保持着较为稳定的状态,垂直活动速率主要集中在0.09~0.69mm/a,水平走滑速率在0.20~1.40mm/a.整体而言,程海-宾川断裂带中多数断裂的第四纪活动性以“中等”和“弱”为主.但历史地震活动表明,其不同段落上的未来强震活动趋势值得关注,尤其是历史强震活动相对空缺的中南段.

Chenghai-Binchuan fault zone in the southeastern margin of the Qinghai-Tibet plateau,which has a composite activity manner of vertical and horizontal left-sliding movement.It plays an important role in regulating the internal matter in the Qinghai-Tibet plateau,and controlling the major strong earthquake activity in the region.Extracting the region tectonic landformsinformation from the RS(remote sensing)images and DEM(digital elevation model)to quantitative study of tectonic geomorphology of the fault zone.The results show that the fault belt have the characteristics of segmented partitions.The northern boundary faults of the Jinguan-Chenghai basin are dominated by normal faults,and they have the highest vertical movement rate in the zone.Qina faults are dominated by strike-slip movement,which have the highest strike-slip activity rate.The eastern boundary faults in Binchuan basin are also dominated by normal faults.The vertical activity rate is lower than that of the northern section.Comprehensive analysis shows that the Quaternary vertical activity of Chenghai-Binchuan fault zone is lower from north to south,and strike-slip activity in central is strongest,diminishing to south.The long-term activity rate of Binchuan fault zone has maintained a relatively stable state,the vertical activity rates between 0.09-0.69 mm/a.Horizontal strike-slip rate between 0.20-1.40 mm/a.The Quaternary activity of faults mainly is"medium"and"weak",but the future earthquake risk should not be ignored,especially in the south middle of it.