A statistical analysis on Wenchuan aftershock activity triggered by tidal is systematically studied based on Schuster＇ s test,including earthquakes triggered by tidal force,tidal stress and tidal coulomb failure stress.The results show that a group of strong aftershocks which occur at the end of July to early August in 2008 at the north of the Wenchuan are obviously triggered by earth tide.The same conclusion is drawn by Schuster＇ s smooth test of the tidal force,tidal stress and tidal coulomb failure stress.In addition,Wenchuan aftershock activity is obviously triggered by fortnight tide.In the north,the aftershocks happened more frequently in the first quarter and the last quarter of the moon,and in the south,the aftershocks happened more frequently in the first quarter and the last quarter of the moon and the full moon.[著者文摘]