Triggering relationship in strong earthquake sequence around the Bayan Har block and its tectonic significance based on Coulomb stress changes and seismicity

Seven major earthquakes of M_W≥6.5 have occurred around the Bayan Har block in the Tibetan Plateau since this century, including the devastated 2008 Wenchuan earthquake and the recent 2017 Jiuzhaigou earthquake. Here we investigate the triggering effects among those major earthquakes by calculating the Coulomb stress changes and analyzing the background seismicity rate changes, and furthermore to understand the tectonic activity of the Bayan Har block. Our results show that, the Coulomb stress changes positively correlate with the background seismicity rate changes. Also, the results show that the Wenchuan earthquake triggered the Lushan earthquake and delayed the Jiuzhaigou earthquake. Besides, there is no significant triggering/delay effect among other major earthquakes. These findings imply that the remarkable earthquake sequence results from the southeastward movement of the Bayan Har block, and the Bayan Har block is still in the highly active seismic period. Furthermore, the seismic hazards of the Bayan Har block and its adjacent faults in the southwestern China should be paid more attention.