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

In this paper, the research on the principal active fault in Binchuan area was conducted through satellite remote sensing interpretation and surface investigation, and then some new opinions concerning the active structural system of this area were put forward. 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's left-lateral and pull-apart tectonic movement pattern in the context of the holistic clockwise rotation of the Tibetan Plateau. 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.