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Title:: Research on Characteristics of Late Quaternary Activity of the North Wenshan-Malipo Fault

Author(s):: ZHOU Qingyun¹; ZHANG Peiquan²; LI Jianlin²; YU Jianqiang¹; (1.Earthquake Administration of Yunnan Province, Kunming 650041, Yunnan, China)(2.Seismological Bureau of Guangxi Zhuang Autonomous Region, Nanning 530022, Guangxi, China)

Keywords:: Wenshan-Malipo Fault; aero photogrammetry interpretation; tectonic geomorphology; terrace

摘要:: 利用航片解译结果并结合野外地质调查,对文山—麻栗坡断裂(简称文麻断裂)北段的地震地质特征进行研究。解译结果显示,断裂沿线活动构造地貌清晰,主要表现为断层陡坎、断陷盆地、水系同步右旋位错等; 影像上线性特征明显而平直,构成(文山)盆地与基岩山地的界线。野外地震地质调查结果显示,该断裂在热水寨切错了T₂阶地堆积,被错地层光释光(OSL)测年结果为(18.1±0.5)ka B.P.,文山盆地北5 km处同样断错T₂阶地堆积,其 ¹⁴C年龄为(15.67±0.05)ka B.P.。以上结果表明,该断裂在晚更新世有过明显的活动迹象,运动性质为右旋走滑兼正断。

Abstract:: Combined the new interpretation of aerial photos with the field geological survey, we investigated the seismic geological characteristic of the northern section of Wenshan-Malipo Fault(Wen-Ma Fault). The interpretation results showed that there is the clear active tectonic geomorphology along the fault, which was mainly manifested as fault scarps, fault basin, river system synchronous dextral dislocations etc.. The linear features on the image are very clear and straight, forming the boundaries between Wenshan basin and bedrock mountains. According to filed seismic geological survey results, we find that the fault in Reshuizhai disrupts T₂ accumulation terrace, and the Optically Stimulated Luminescence(OSL)dating of the disrupted strata suggests an age of(18.1±0.5)ka B.P.. While in the area of the distace of 5 km to the north of Wenshan basin, the radiocarbon dating(¹⁴C)of the disrupted T₂ accumulation terrace shows an age of(15.67±0.05)ka B.P.. In conclusion, the Wen-Ma Fault has clear signs of activities in the late Pleistocene, which is dominated by dextral strike slip with normal slip component.