Static Stress Triggering Effects Related with M8.0 Wenchuan Earthquake

In this article, firstly, we calculated and analyzed the patterns of Coulomb stress changes induced by a sequence of strong earthquakes that occurred in Songpan (松潘), Sichuan (四川) Province in 1973 and 1976, and discovered that the Ms8.0 Wenchuan (汶川) earthquake of 2008 was epicentered in a relevant Coulomb stress triggering zone. This suggests that the Coulomb stress on the middle and southern segments of the Longmenshan (龙门山) fault zone increased after the Songpan sequence of strong earthquakes, and the stress increment might cause the 2008 Wenchuan earthquake having already occurred somewhat ahead of time. Further, we calculated and analyzed Coulomb stress changes coinduced by both the Songpan sequence and the Ms8.0 Wenchuan mainshock. The result shows that the Ms6.4 Qingchuan (青川) earthquake of May 25, 2008 on the northeastern segment of the Longmen-shan fault zone was triggered by the Wenchuan mainshock, and that the southwestern segment of the fault zone is also in the stress triggering zone. Besides, the Maoxian (茂县)-Wenchuan fault (i.e., the back-range fault of the Longmenshan fault zone), which extends parallel to the seismogenic fault of the Wenchuan earthquake, is in a shadow zone of the Coulomb stress changes, and therefore, its potential hazard for producing a strong or large earthquake in the near future could be reduced relatively.