Abstract: The Heihekou fault, being apart 30 km from Zhangye in the southwest, is a reversed fault which trends to the northwest and dips to the southwest. It is found that the fault on a natural section along the bank of the Heihe River dips steeply to the southwest, and that the Ordovician system thrusts to the northe-ast on the Late Pleistocene alluviam with a throw of 17m. A fault scarp was formed in the fault movement on terraces of the Heihe River. The terrace withan estimated age of 5 ka B.P. is vertically dislocated by 2m, age of 10 ka B.P. by 4m, and age of 13 ka B.P. by 9m. These dislocations and the sediments near the fault indicate there had been 3 movement enents at least. The vertical dislocationis 2～5 m each, the average recurrence interval is 3～5 ka, and the average slip rate is 1.67～0.4 mm/a.

Key words: Heihekou fault, terrace dislocation, recurrence interval, slip rate

摘要： 黑河口断层位于张掖西南约30km，是一条走向北西，倾向南西的逆断层。黑河沿岸的一个天然剖面上见断层面向南西陡倾，奥陶系向北东逆冲于晚更新世河流砾石层之上，垂直断距17m。断层活动在黑河阶地上形成了一个断层陡坎。年龄约为5kaB.P.的阶地被垂直错断2m，年龄约为１０10kaB.P.的阶地被垂直错断4m，年龄约为13kaB.P.的阶地被垂直错断9m。这些错距及断层附近的沉积物反映断层至少有3次活动，每次活动的垂直位移为2～5m，活动时间间隔为3～5ka，平均活动速率为1.67～0.4mm/a。

关键词: 黑河口断层, 阶地位错, 活动周期, 活动速率