The Xiadian Fault is a very important concealed active fault in the Beijing Plain. It is the seismogenic fault of the Sanhe-Pinggu MS8. 0 earthquake in 1679. The ancient earthquake sequence in the long historical period is of great significance to understand accurately the activity characteristics of the fault and effectively reduce the earthquake disaster risk in Beijing. We have re-interpreted the Dahuzhuang trench,and identified three layers of buried paleosol,six collapsed wedges and one sand liquefaction event. Further,through the comparison with the landmark strata and paleo-earthquake events revealed by other trenches on the fault,an ancient earthquake sequence with a long historical period of the Xiadian Fault was established:since the 31 ka,the Xiadian Fault has 11 occurrences of earthquake events(including the 1679 earthquake),and the average recurrence interval is about 2. 8 ka. The paleo-seismic sequence also shows that there is an ancient earthquake cluster period from 25 ka to 15 ka,and there are 5 strong earthquakes in the cluster period.The average recurrence interval is about 2. 0 ka,which reflects the phase difference of the Xiadian Fault activity.
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