Earthquake-Tide Correlation

The detection of moonquakes that occur when the Moon is at perigee has prompted a search for tidal effects on earthquake occurrences. An attempt was made to correlate earthquakes listed in the CGS-NOA epicentre determinations with the tidal phase of semidiurnal tides. This study was confined to several seismic regions representative of tectonic and nontectonic regions. An extended form of Schuster's test was used to decide whether significant correlations existed. Though some tidal influences could be accepted at a 5 per cent significance level, the effect was not consistent or stable with time. Earthquakes, if they are affected by tides, show a slight tendency to occur at times when the tidal stress is changing most rapidly. Insufficient data was available to compare tectonic to non-tectonic areas.