关键词: 活动断裂, 地震地表破裂, 阿尔泰

Abstract: The active faults in Altai Mountains are mainly in NW—NNW direction and can be divided into three belts:the western margin of Altai Mountains active fault zone, the central Altai Mountains active fault zone and the eastern margin of Altai Mountains active fault zone. The eastern marginal active fault zone consists of two right-lateral strike-slip faults,the Hovd active fault and the Har-Us active fault,and the compressional basins between them. Several segments of earthquake ruptures have been reported along the strike-slip faults in former studies. We also found two new segments of earthquake rupture on the middle to south parts of the fault zone in recent field investigation. One segment is on the Jargalant Fault in the middle part of the Har-Us Fault zone,the other segment is on the Tugen Gol Fault in the south part of the Hovd Fault zone. The earthquake surface rupture on the Jargalant Fault has been studied in more detail in this paper. The rupture zone is 50km long with about 4～5m dextral displacement,implying a large and recent earthquake. Earthquake ruptures have been observed on each segment of the eastern margin of Altai Mountains active fault zone. So,the eastern margin of Altai Mountains is a strongly active tectonic zone with large earthquake.

Key words: active fault, earthquake rupture, Altai