Abstract: By applying monthly earthquake catalogue reported from Fujian, this paper studied the effect of lunar phase associated with aftershock activity of Taiwan Strait earthquake with Ms7, 3, which occurred on 16 Sep. 1996. The statistic results on frequency of earth­quakes wi,th a certain magnitude show that the changes of aftershock sequence in Taiwan Strait within the synodic month are fluctuated, and the fluctuation is obviously modulated by the lunar phase. The change of fluctuation reaches the relative limitation around the new moon, full moon, first and last quarters, while the amplitude of the frequency fluctu­ation can be as much as more than 80 percent of the average frequency of seismicity. All of these facts proved the existence of the lunar phase effect of aftershock activity, and this in­fluence can't be neglected. Additionally, the results of harmonic analysis of the lunar phase effect also show that the lunar phase effect of aftershock sequence is characteristic of the periodicity of one fourth month and half month. It is scientifically meaningful and practical to study the lunar phase effect of aftershock on strong aftershock prediction and the change of regional stress field.

Key words: Aftershock activity, Effect of lunar phase, Modulation, Taiwan Strait