Abstract: There is an obvious difference between the durations of strong aftershock sequences for ten large mainshocks with magnitude of 6.9 or more occurred in North and Southwest China during 1966—1981.The durations range from one day to one thousand days and are seemingly independent of mainshock magnitudes. The durations are related to the recurrence interval of the large shocks,the longer the duration,the longer the recurrence interval.From the view point of earthquake mechanics,a longer recurrence interval indicates a longer static contact of the fault plane,resulting in the increase of frictional strength,as well as the number and area of asperities. Therefore,a longer duration of strong aftershock sequence (ruptures of remainder strong asperities) after mainshock would be observed.

Key words: Duration of strong aftershock activities, Recurrence interval, Earthquake mechanics

摘要： 1966—1981年中国大陆华北和西南地区发生了10次大地震(M_s≥6.9),其强余震活动持续时间有明显差异,从1天到1000天不等。它们似乎与主震震级大小无关,却依赖于不同主震的重复时间,即较长的持续时间对应较长的重复时间。基于地震力学的观点,较长的重复时间意味着地震断面静止接触时间较长,断面摩擦强度将增大,产生数量较多和面积较大的强固点,所以,有可能在断面主破裂之后,观测到较长持续时间的强余震活动(强固点破裂)。

关键词: 强余震活动持续时间, 重复时间, 地震力学