西秦岭北缘断裂带武山-天水段全新世活动的新证据

摘要

The western segment of Zhangxian along the Western Qinling active fault zone is a large left-lateral strike-slip active fault zone and a historical strong earthquake zone.Recent studies on this area have obtained the latest geological and geomorphological information.However,the latest age of tectonic activities among the segment of Wushan—Tianshui and Tianshui—Baoj i is still unclear.In this paper,the Wushan—Tianshui segment is studied in detail using high-resolu-tion satellite images,geomorphological analysis,trenching technology,and 14 C radiocarbon dat-ing technology.Results suggest that tectonic activities since the late Quaternary are remarkable. Geomorphic expressions include fault-controlled valleys,sinistral offseted ridges and stream,and fault scarp.A consequence in more trenches and dated 14 C samples reveals that stratum from the Holocene have been raptured by the latest tectonic activities.Thus,this study provides new evi-dence for Holocene tectonic activities of the Wushan—Tianshui segment of Western Qinling fault.%西秦岭北缘断裂带是青藏高原东缘一条大型左旋走滑活动断裂带和历史强震带。前人对该断裂漳县以西段曾开展过大量研究工作，获得其最新构造活动的地质地貌证据，而中段（武山—天水段）和东段（天水—宝鸡段）最新活动时代一直存在分歧。基于高分辨率卫星影像解译、地质地貌调查与综合分析、探槽开挖和14 C测年等方法，对西秦岭北缘断裂带武山—天水段进行详细研究，结果表明：该段断裂晚第四纪以来活动显著，地貌上主要表现为断层垭口、断层沟槽、山脊与水系及阶地同步左旋位错、断层陡坎等；多个探槽剖面及测年结果显示其最新构造活动断错了全新世地层，为该段断裂全新世活动和大震危险性分析提供了新的证据。