Abstract: There are geological and microgeomorphological evidences that for the Haiyuan fault there have been 5 major earthquakes with a magnitude of about 8.5 since the Holocene,among which the earthquake of 1920 is the latest.The ¹⁴C dates forthe others are 3680?60,6300?70,7830?>103 and 9360?75 B.P..respectively.It can be found that there has been an evident increase of the interoccurrence time for these events since that time.

摘要： 地质证据和微地貌证据表明,全新世以来海原断层共发生过五次8.5级左右的大地震,1920年海原大地震是它们中最晚的一次。其它大地震的¹⁴C年代分别为距今3680±60年;距今6300±70年;距今7830±>103年(内插);距今9360±75年。可以看出全新世以来,大地震的重现间隔是明显增加的。