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由于南华山北麓断裂带的新活动,使得南华山北麓菜园—乱堆子16公里范围内的21条冲沟发生明显断错,显示出左旋位移指向。本文研究了这些断错冲沟的地质地貌表征、断错冲沟的发育过程和断错量,并根据晚更新世以来沉积物的~(14)C年龄和区域冲沟的溯源侵蚀速率,计算出晚更新世以来南华山北麓断裂带的平均滑动速率为4.3毫米/年;同时,量测出1920年海原8.5级地震震中区地震断层的最位移量为6.9米。根据以上资料,估算出南华山北麓断裂带8.5级强震的重复率约为1600年。
Due to the new activity in the northern foot of the South Huashan fault, 21 gullys within the range of 16km from the vegetable garden in the northern foot of Mt.Nanhuashan were obviously interrupted and showed a left-handed displacement. In this paper, the geological and geomorphological features of these fault gully, the development of fault gully and the amount of fault truncation are studied. Based on the ~ (14) C age of sediments and the traceable erosion rate of regional gully since the late Pleistocene, Since Late Pleistocene, the average sliding rate of the fault zone in the northern foot of Mt.Nanghua has been 4.3 mm / year. At the same time, the maximum displacement of the earthquake fault in the epicenter area of Haiyuan-M 8.5 earthquake in 1920 was 6.9 meters. Based on the above data, it is estimated that the repetition rate of the 8.5 magnitude strong earthquake on the northern foot of Mt.Nanghua is about 1600 years.