Abstract: Under the instruction of seismogenic model of group earthquakes, characteristics of seismological and precursory anomalies of group earthquakes with M≥6.5 in Chuan-Dian area are analyzed. It shows that group earthquakes with M≥6.5 in Chuan-Dian area always occur in the active period of strong earthquakes, in this period the measured values of several Hg content in groundwater changed dozens even hundred times higher than normal value. The anomalies were much higher than those in the quite period of strong earthquakes. The seismicity increased 1~2 years before the occurrence of the group earthquakes over an extensive area. More than 30% of precursory anomalies changed consistently and there was no turning variation when the first earthquake occurred. As far as the single earthquake and the last earthquake of group earthquakes concerned, the number of anomalies appeared before the occurrence and changed consistently while no turning after the occurrence were less than and equals to 15%. The anomalies of the first earthquake were more than those of the last earthquake of group earthquakes.

Key words: Group earthquake, Judging indexes, Chuan-Dian area