Tidal triggering of seismicity in the region of Palu, Central Sulawesi, Indonesia

This paper investigates the correlation between tidal stress and earthquakes for periods ranging from hours to months in the limited zone of the Palu region (Central Sulawesi, Indonesia). Through Schuster and binomial tests, we examined the relation between the seismicity (time density of seismic events) and tidal potential arising from the Moon and Sun, using all tidal components simultaneously and focusing on the estimation of specific terms. The results show significant correlations between the seismicity and tidal potential for S2 (0.5 d) and O1 (1.075 d) tidal components in the case of solely isolated earthquake events, particularly for shallow earthquakes. Meanwhile, there is a strong relationship between aftershocks and tidal components larger than the Mf period (13.661 d). Finally, the analysis of the temporal variation of the earthquake-tide relation reveals an optimal correlation for about six years before the 2018 great Palu earthquake. The correlation becomes insignificant afterwards.