Abstract: Based on the measurements of the positions of knickpoints in the gullies passing throngh pluvial fans,this paper deals with the factors that influence the headward migra tion rate of knickpoints in the gullies dissecting the east piedmont fans of Helanshan Mt. The relation between the position and age of knickpoint hasbeen established. The result shows that at least 3 prehistoric events of magnitude,as large as that of 1739 Pingluo earthquake have occured along the eastern Piedmont fault of Helan Mountain since Holocene. The recurrence interval of great earthquakes in this area is determined to be 2500-3500 years.

Key words: Eastern piedmont of Helanshan Mt., Knickpoint, Fault scarp

摘要： 本文通过对洪积扇断层崖上升盘冲沟裂点位置的实测和研究,讨论了贺兰山东麓地区影响裂点溯源迁移速率的主要因素,建立了这一地区裂点位置与形成年龄关系的公式。据此确定贺兰山东麓断层全新世以来至少发生过三次类似1739年平罗大地震的古地震事件,强震的重复间隔时间大约在2500年至3500年。

关键词: 贺兰山东麓, 裂点, 断层崖