关键词: 古地震, 复发间隔, 最晚事件, 安宁河断裂带

Abstract: Surface rupture traces of several large paleoearthquakes are found along the Xiaoxiangling Mountain segment of the Anninghe fault zone. Trenches are excavated across the main fault at two sites to investigate later Holocene paleoearthquakes of this fault segment. The results show that at least 4 paleoseismic events with surface ruptures occurred on the fault segment during the last 2 300 years, suggesting an average recurrence interval of 600 to 700 years. Through carrying out the dendrochronologic calibrations of the ¹⁴C ages of 4 samples taken from micro stratum-units lian over and under the latast event's horizon, and analyzing the probability distributions for the calendric dates from the calibrations, the date of the latest event here is bracketed sometime in the 15th century.Further,combining the fragmentry documented record of an ancient earthquake for a nearby town,it is believed that the latest event occurred possibly in the year of A.D. 1480. This event produced an average left lateral offset as much as 3 meters along the surface fault. Such an amount of mean coseismic offset is comparable with those yielded by large strike-slip earthquakes with moment magnitude 7.5?0.3.

Key words: Paleoearthquake, Recurrence interval, Latest event, Anninghe fault zone