It is a basic fact that earthquake occurrence can be modulated and triggered by the syzygial tide.

朔望潮调制地震的生已是一个本事实。

The syzygial tide is that the maximum amplitude period of semi-monthly tide added to the semi-diurnal and full-diurnal tides.

朔望潮即是半月潮大时段再迭加半日潮全日潮。