Re: Is there a co-relation between Earthquakes and full moons?

Dear Kjose,

Thank you for writing.  The affect of the moon on the earth is obvious when 
we see the daily changes brought about by the ocean tides.  Thus, it seems 
natural that the lunar cycle also could affect the solid parts of the 
earth.  However, most seismologists currently agree that the lunar cycle 
(full moon or new moon) does not increase the frequency of earthquakes nor 
cause extremely strong earthquakes.  

If earthquakes are triggered by the full moon, then seismologists should be 
able to recognize that large earthquakes are occurring every month, on a 
regular and predictable pattern.  To date, this has not been observed 
despite the dense network of monitoring stations around the world and a 
large historical record.  One geologist does claim success in predicting 
strong earthquakes based upon the alignment of the Moon and Sun with the 
Earth, such as during eclipses.  However, strong earthquakes also occur 
when they have no particular alignment!  

This is not to say that Earth is not affected by the Moon’s movement! The 
gravitational attraction of the Sun AND the Moon on the Earth cause it’s 
surface to bulge slightly toward them.  Volcanologists use these very 
slight and slow ground movements called earth 
tides  to calibrate their monitoring instruments.  Earth tides don’t appear 
to trigger earthquakes but they may trigger eruptions.  
 
Last but not least, it may make more sense to expect stronger earthquakes 
during a new moon rather than the full moon.  During the full moon, the 
Moon and the Sun are on opposite sides of the Earth.  Their 
gravitational forces pull Earth from two opposing directions, canceling 
each other to a degree.  But, the new moon occurs when the Moon and the Sun 
are located on the same side of the Earth.  The combined gravity of 
both bodies pull the Earth from one direction.

Thanks again for the question.