The collected data of earthquakes since 1993 are divided into two sample groups of grade 5 and grade 6 respectively. Based on the cluster analysis method of fuzzy equivalence relation

these earthquakes are classified into different classes according to three parameters

i.e.

earthquake fault

earthquake source complexity and apparent stress

and the characteristics of isolated earthquake

main shock-after shock earthquake and multiple earthquake are studied. It can be concluded: 1) isolated earthquake features simple earthquake dislocation mode

high or very high stress drop

low or very low apparent stress and low heterogeneous level of medium in earthquake source region; 2) multiple earthquake （strike-slip） features complex earthquake dislocation mode

low or very low stress drop

high or very high apparent stress and high heterogeneous level of medium in earthquake source region.