Abstract: According to difference of magnitude between the largest and second largest earth quakes, the earthquake sequences are divided into four types, i. e. the single major shock, major-after shock, double major shock and multiple major shock. The results of division from 143 earthquake sequences in China's continent show that: the single major shock takes 14 % , the major-after shock takes 5 9 % , the double major shock takes 13 % , and the multiple major shock takes 14 % . The b -value of earthquake sequences are related to major shock magnitude and type of sequences. It is increased with the raising magnitude of major shock as the same type. Under similar major shock magnitudes, b -value of single major shock is the smallest, b -value for types of major-after shock and double major shock are medial with small difference, b -value of multiple major shock type is the largest, no matter what if the major shock magnitude is 7 or 6. The possibility to predict the long-term ten­dency of strong earthquakes by using the b -value change in the earthquake sequences with M = 7 is also discussed.

Key words: Earthquake sequence, Type of earthquake sequences, b -value, Long-term tendency of strong earthquake