Abstract:In order to locate the dangerous region for annual determination of seismic background, the relationship between the three parameters of future strong earthquakes and the moderate earthquake concentrating regions in the Tianshan seismic zone is analyzed. The results show that most strong quakes occur in the concentrating regions and their borders, especially the borders,and magnitude of strong earthquakes is related to the concentrating region size. The principle of determining the concentrating region is that length of the concentrating region is larger than 150 km and the number of earthquakes in the region is equal to or larger than 4.Further more,the relation among the source size, seismogenic zone size, concentrating region size and anomaly area size is discussed. It is considered that upper and lower limits of the concentrating region size are the anomaly area size and seismogenic zone size respectively.