A review of tidal triggering of global earthquakes

Earthquake prediction remains a challenging and difficult task for scientists all over the world. The tidal triggering of earthquakes is being proven by an increasing number of investigations, most of which have shown that earthquakes are positively correlated with tides, and thus, tides provide a potential tool for earthquake prediction, especially for imminent earthquakes. In this study, publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes, which were classified into three main types: tectonic, volcanic, and slow earthquakes. The results reveal a high correlation between tectonic earthquakes and tides (mainly for semidiurnal and diurnal tides; 14-day tides) before and after the occurrence of significant earthquakes. For volcanic earthquakes, observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces, mostly those with semidiurnal and diurnal periods. For slow earthquakes, the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal tides. In conclusion, the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism, and thus, the prediction of these types of earthquakes should be investigated. However, there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all earthquakes. The main inadequacies are discussed in this paper from our point of view.