中国大陆第5地震轮回青藏块体强震活动特征

1977年以来（中国大陆第5地震轮回）青藏块体发生11次7级以上地震，分析7级以上地震及地震前5级以上地震活动特征，结果表明，7级以上主震发生前，震中区5级以上地震活动一般存在20年以上的平静异常，地震活动特征差异与主震震源机制解及构造位置密切相关。

The characteristics of seismic activity of strong earthquakes of Qinghai-Tibet block in the fifth earthquake cycle in mainland China

There have been 11 earthquakes with M_S ≥ 7.0 in the Qinghai-Tibet block since 1977. The seismic activity characteristics of earthquakes with M_S ≥ 7.0 and earthquakes with M_S ≥ 5.0 before earthquakes with M_S ≥ 7.0 in the Qinghai-Tibet block are analyzed. The results show that, before the main shock in epicentral area, there generally is calm anomaly of M_S ≥ 5.0 seismic activity of earthquakes with duration of more than 20 years. The characteristics of seismic activity of earthquakes with M_S ≥ 5.0 before main earthquake are closely related to the seismic source mechanism and tectonic location of the main earthquake.