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

摘要： 阿尔泰构造带的活动断裂主要为NW—NNW向。按构造位置可分为阿尔泰西缘活动断裂带、阿尔泰中央活动断裂带和阿尔泰东缘活动断裂带。阿尔泰东缘活动构造带由科布多(Hovd)活动断裂带、哈尔乌苏湖(Har Us)活动断裂带2条大型右旋走滑活动断裂和中间的挤压盆地带构成。在2条走滑断裂带上,前人发现多处地震地表破裂带。通过对阿尔泰东缘构造带中南段地区的野外调查,在哈尔乌苏湖断裂带中段的Jargalant断裂、科布多断裂带南段的Tugen gol断裂上新发现地震地表破裂带。其中,沿Jargalant断裂地震地表破裂带长约50km,右旋位错量约4～5m,是一次规模大、活动较新的破裂事件。可见,在阿尔泰东缘活动断裂带的不同断裂段上均有保存较好的地震地表破裂,显示阿尔泰东缘是活动强烈的地震构造带。

关键词: 活动断裂, 地震地表破裂, 阿尔泰