Abstract: There have been 5 earthquakes with magnitude above M_S7.0 since 2000 in Xinjiang and its surrounding areas. After these strong earthquakes, local stress in Xinjiang will be redistributed, which lead to the increase of the rate of small earthquakes activities in some areas, Such as Urumqi in Xinjiang Tianshan seismic zone, in which small earthquakes with magnitude above MS 1.6 raised after the 21 March 2008 M_S7.3 Yutian, Xinjiang earthquake. Through the analysis of space-time scanned images for z-value and b-value in these regions affected by strong earthquake activities. The research results show that: ① The change of negative z-value and b-value area is consistent before and after strong earthquakes. ② A preliminary study suggests that the increase of small earthquake activity rate for local area and its forthcoming moderate earthquake, which are related to the magnitude of strong earthquake and epicenter distance, the greater the magnitude of strong earthquake, the shorter the time interval, the closer the distance, then the rate of small earthquake activities increases more obviously, and the intensity of its corresponding medium-earthquake is likely to be greater.

Key words: Strong earthquakes, Small earthquake activity rate, z-value, b-value, Xinjiang region