Spatial Distribution Characteristic of the b-value in Dabie-Sulu and Its Adjacent Areas

The Tanlu( Tancheng-Lujiang) fault is one of the major structures in eastern China,which cuts across different blocks and controls the tectonic activity. Using the seismic data from the China Earthquake Networks Center,we investigate the spatial variations of the b-value in the Dabie-Sulu( Jiangsu-Shandong) organic belt by calculating the b-value of each grid( 1°×1°) from 1970 to 2010. The study shows that: the b-value is smaller in the Tanlu fault and its adjacent area,which might suggest that the major earthquake recurrence period is relatively long due to the lower frequency of small earthquake activity. In both sides of Tanlu fault,the b-value is higher at the edge of Sulu block and the eastern part of Dabie orogenic belt. The b values are higher in North China central orogenic belt,and small earthquake activity which occurred along the central orogenic belt is frequent. Additionally,combined with geological and geophysical study,we find that the b-value has a certain correspondence relationship with the lithologic distribution,which informs us that seismic activity features are closely related to the inhomogeneous media in the crust.