滇西北宾川地区主要活动断裂及其活动构造体系

The main active faults and the active tectonic system of Binchuan area,northwestern Yunnan

通过卫星遥感解译和地表调查,对滇西北宾川地区活动断层进行了相对全面的调查研究,并对该区活动构造体系提出了新认识。研究表明,该区发育以北东向正断层和走滑断层为主的活动断裂,并构成了典型的张扭性帚状构造,控制了宾川地区构造地貌的发育。该活动构造体系的主干活动断裂是近南北向程海—宾川断裂向南至宾川处分解后形成的2条分支断层,即近南北向以正断性质为主兼具左旋的宾川断裂(F1)和北东向左旋走滑的上沧—鱼棚断裂(F2)。宾川地区活动构造体系是在区域近东西向伸展和微地块顺时旋转的共同作用下形成的,反映了滇西北裂陷带在青藏高原整体瞬时旋转背景下的左旋拉分运动模式。同时,对宾川地区活动构造体系的研究也有助于更好地认识该区未来的强震危险性,对于其中主干断裂(F1、F2)的大震危险性应给予更多关注。

In this paper, the research on the principal active fault in Binchuan area was conducted through satellite remote sensing in？terpretation and surface investigation, and then some new opinions concerning the active structural system of this area were put for？ward. The results achieved by the authors show that there are mainly NE-trending normal faults and strike-slip faults in this area, which constitute a typical transtension brush-structure and results in the geomorphical evolution of Binchuan area. The major faults of this active structural system are two splay fractures divided by the NS-trending Chenghai fault when the fault extended southward to Binchuan：the NS-trending Binchuan fault （F1） which has both normal and left-lateral strike-slip features, and the NE-trending Shangcang-Yupeng left-lateral strike-slip fault （F2）. The formation and evolution of Binchuan′s active structural system was under the joint action of the regional EW-trending extension and the clockwise rotation of the micro-massifs, which reflected the NYRZ＆#39;s left-lateral and pull-apart tectonic movement pattern in the context of the holistic clockwise rotation of the Tibetan Pla？teau. Meanwhile, the survey of the active structural system will contribute to understanding the future seismic risks in Binchuan area, and it is suggested to pay more attention to the risk of principal faults for strong earthquake.