Abstract: Based on the focal mechanism solutions of M_L≥3.0 earthquakes from January 2000 to June 2014 in Sichuan area, the focal mechanism type and stress field of every sub-blocks and different fault zones are analyzed. Take the 2008 Wenchuan 8.0 and the 2013 Lushan 7.0 earthquake for example, we study spatial-temporal evolution characteristic of main compressive stress in the sub-blocks of Sichuan before and after the two strong shocks. The major results are: (1) the focal mechanism types in the sub-blocks of Sichuan are relatively in disorder, which may reflect the complexity of internal structure in blocks, and that focal mechanism solutions of earthquakes along fault zones are relatively in singleness, which are consistent with the dislocation type of fault. (2) The stress direction of the sub-blocks and fault zones in Sichuan shows good consistency, the dominant orientations presents in NW and NNW, and the dip angle is close to horizontal. (3) before the Wenchuan 8.0 and Lushan 7.0 earthquake, the main pressure stress orientation of Sichuan—Qinghai block and middle-south sections in Longmenshan fault zone all appear good consistency,which is in NW direction, and after the Lushan 7.0 earthquake, the main pressure stress orientation in Sichuan—Qinghai, Central Sichuan blocks and the Longmenshan fault zone turn into NE direction.

Key words: Regional stress field, Focal mechanism solution, The Sub-block of Sichuan area