Abstract:In this study, we statistically analyzed 51 earthquake sequences with magnitudes ≥ 5.0 that occurred in eastern Northwest China from Jan. 1970 to Dec. 2012. Of these, the strike-slip type occurred 30 times, representing 58.8% of the total. The overlap and inverse-impulse type occurred ten times, representing 19.6%, and the normal fault type occurred six times, representing 11.8%. With respect to earthquake rupture type, the mainshock-aftershock type represented more than 60% of the rupture types, followed by the isolated type, and lastly the double shock or multiple shock type. With respect to normal-fault-type earthquakes, the mainshock-aftershock type had the highest proportion at 50%. The next highest proportion was the double shock or multiple shock type at 33.3%. The isolated type was least frequent. For earthquakes of the same rupture and sequences types, a linear relation between the main shock magnitude and the greatest aftershock magnitude was most common. Also, the relation was weak between the main shock occurrence time and the greatest aftershock occurrence time. More than 60% of the strike-slip and inverse-impulse types experienced the greatest aftershocks one day after the main shock but only 16.7% of the normal fault type experienced the greatest aftershocks one day after the main shock. If a sequence cannot be categorized as a double shock or multiple shock sequence, the empirical equation ΔM=1.54×M-6.53 can be used to analyze the greatest aftershock.