Earth tides and Etnean volcanic eruptions: an attempt at correlation of the two phenomena during the 1983, 1985 and 1986 eruptions

Abstract An attempt has been made to correlate volcanic events on Mt. Etna and Moon-Sun attraction during the eruptions of 28 March–6 August 1983, 12 March–13 July 1985 and 30 October 1986. The possibility of a ‘trigger’ effect has been supposed for eruptive phenomena that originate by small and continuous external forces under particular stress conditions on the volcanic structure. The parameters compared, for the two phenomena, are the hourly mean tremor amplitude recorded at Serra La Nave station and the hourly value of the vertical and of the two partial horizontal north-south and east-west components of the tidal acceleration induced by the Moon-Sun system. The relationship between two series of values (the former for the tremor amplitude and the latter for one of the tidal acceleration components) were then tested by statistical methods based on the information theoretic measure of interdependence between any pair of signal sequences. The results show an effect of the horizontal tidal components on well-known tectonic structures, which may be widened or closed; in contrast, there is little evidence that the uprise of magma masses might depend on the vertical tidal attraction.