Hi All. The following is from the UC Berkeley Seismological Laboratory. Take Care…Don in creepy town

Can the position of the moon affect seismicity?

The question often arises as to whether astronomical events, such as planetary alignments, can significantly influence the occurrence of earthquakes. The moon, sun, and other planetary bodies in our solar system influence the earth in the form of perturbations to the gravitational field. The relative amount of influence is proportional to the objects mass and inversely proportional to the cube of its distance from the earth. The general idea is that strains in the earths crust caused by perturbations in the gravitational field may influence when an impending earthquake will occur (like the straw that broke the camel's back). If this were indeed the case we would expect to see a correlation between rate at which earthquakes occur and the perturbations to the gravitational field. The dominant perturbation in the earth’s gravitational field generates the semi-diurnal (12 hour) ocean and solid earth tides which are primarily caused by the moon (due to its proximity) and the sun (due to its large mass). No significant correlations have been identified between the rate of earthquake occurrence and the semi-diurnal tides when using large earthquake catalogs. There have, however, been some small but significant correlations reported between the semi-diurnal tides and the rate of occurrence of aftershocks in some volcanic regions, such as Mammoth Lakes.

The relative influences of object in the solar system, in order of magnitude. Are:

Object Mass
(Earth=1) Distance
(Million km) Relative Influence
(Moon=1)
Moon 0.01228 0.38 1.00
Sun 329390 149 0.45
Venus 0.8073 41 0.000052
Jupiter 314.5 629 0.0000056
Mars 0.1065 79 0.00000096
Mercury 0.0549 91 0.00000033
Saturn 94.07 1277 0.00000020
Uranus 14.40 2720 0.000000004

The combined influence of the rest of the objects in the solar system is less than 10 billionths of the influence if the moon. The combined influence of all objects in the solar system, other than the moon and the sun, is at most 0.000059 or only 1/24500 the combined influence of the moon and the sun. Thus even when all the planets are lined up, their combined influence is relatively small.

Besides the dominant semi-diurnal periodicity, there are other significant periods. Most notably, there is the synodic month (~29.53 days) periodicity due to the moon's orbit around the earth (relative to the sun) and the 18.5 year periodicity due to the 5 degree inclination of the moons orbit. No significant correlations between these periods and the rate of occurrence of earthquakes have been found.

Given the relative influence of a planetary alignment and the lack of correlation of earthquakes with the dominant gravitational effects, we would not expect planetary alignments to significantly infleunce either the rate of occurrence of earthquakes or the relative motion of the tectonic plates. No significant correlations of earthquakes with planetary alignments have been found.

The gravitational influence of the other bodies in the solar system is largest in the vicinity of the earth's equator and smallest near the poles.

• Quake Trackers