Humanity has been blaming the full Moon for a lot of things for a very long time. Modern data analysis has punctured a lot of these myths, including the timing of births and hospital admissions for accidents. (People turning into wolves still to be confirmed). The latest association to be disproven is one between lunar phases and very large earthquakes. For good measure, the same study has also found quakes are unconnected with the time year too.
In the light of the influence the Moon has over the tides, it is not ridiculous to think its gravity could be pulling on the Earth's crust enough to cause it to shake, or even that the extra weight of water could trigger disturbances beneath the oceans.
Although the amount of light the Moon reflects onto the Earth is unlikely to be important, tides are larger when the Moon and Sun are near each other in the sky, or almost directly opposite, as occurs at new and full Moons respectively. Some studies have claimed to find an association between lunar cycle and earthquake frequency, but Dr Susan Hough of the US Geological Survey noted the relationship was always so weak as to be highly suspect.
Hough tested the data, restricting herself to events of magnitude 8 or larger on the Richter scale, a sample of 204 earthquakes of 400 years. Her results have been published in Seismological Research Letters. Although there were 16 earthquakes from this sample on the seventh day after a new Moon, Hough described peaks such as this as “No different from the kinds of patterns you would get if the data are completely random.” She also noted: “The lunar tides would be at a minimum at this point, so it doesn't make any physical sense."
Similarly, Hough found no tendency for very large earthquakes to congregate on particular days of the year.
Hough does not expect her work to change convinced minds. She notes that amateur earthquake predictors bombarded Charles Richter, as the one well-known seismologist, with claims about the influence of the Moon. “Sooner or later there is going to be another big earthquake on a full moon, and the lore will pop back up," she said. Nevertheless, she hopes studies like hers will give skeptics something to point to when the next wave of such claims occurs.
The belief in the influence of the Moon is so widespread and so easy to test, there is an abundance of studies on the topic. In some cases, an association has been found. You're more likely to be mugged on a moonlit night than a dark one, for example, but physical effects outside the ocean are hard to find.