Major NZ Earthquakes and the Moon

## Major NZ Earthquakes and the Moon

Are major earthquakes related to the position of the Moon? Does the gravitational field of the Moon (and Sun) influence earthquakes on Earth? Recent (N.Z.) media reports have given widespread coverage to local predictions of large earthquakes based on the position and phase of the Moon. Is there a correlation?

16 major (mag. > 6.9) earthquakes in and around New Zealand have been accurately recorded since 1848. Two elements of the Moon are investigated.

• The fractional illumination of the Moon (0 - New, 1.0 - Full),

(determining the relative positions of the Sun, Earth and Moon. A Full Moon will have the relative positions as Sun-Earth-Moon, diluting any gravitational influence from the Moon or Sun. A New Moon will have Sun-Moon-Earth, increasing any Sun+Moon gravitational influence) and

• Earth-Moon distance,

(again, the gravitational influence on Earth by the Moon will be maximised at closest distances)

If the Moon strongly influenced (by its gravitational field) the occurence of major earthquakes then we should expect to see a greater number of major earthquakes near New Moon and when the Moon is at it's nearest approach to Earth.

New Zealand Earthquakes of mag. > 6.9. 16 events have been recorded since 1848. Plotted is fractional illumination of the Moon (x axis) versus Moon Distance from Earth (in units of Earth radii). The latest earthquake, 21 August 2001 (the data point at X=0.03, Y=57.2) is shown at the bottom, left part of the plot.

The earthquake events display a scatter diagram.

• Splitting the 16 data points at 0.5 fractional illumination gives 10 events with <0.5 fractional illumination.
• Splitting the 16 data points at a Moon distance of 60 Earth radii (approximately the average Moon-Earth distance) gives 6 events with distances <60 Earth radii.

Conclusion: Whilst 16 events is not a large sample size, there is no strong statistical evidence for the Moons position or illumination influencing New Zealands major (mag. >6.9) earthquakes.

Glen Mackie

Glen Mackie is Senior Research Fellow, in the School of Physical and Chemical Sciences, Victoria University of Wellington.