GeologyRocks

The idea has some merit. A quake is the result os a release of stress built up over a certain amount of time. The moon's gravitational field will affect the stree field around fault zones. If the fault is close to moving, then the moon could provide the final push...

Just my 2p worth...

EDIT: However, I don't believe that you can predict this....

I don't think it's a daft idea. The Moon's gravitational pull is strong enough to create tides and there's some evidence (from research I was involved in about 35 years ago) that it also creates a tidal effect in rocks. The alignments of joints in the Carboniferous limestones of Yorkshire show evidence of directional control influenced by the moon's gravity. At least that's what we thought at the time. Therefore, it's entirely possible, in my opinion, that the Moon could trigger earthquakes.

Gus

Clearly -- and, to a lesser extent, the Sun as well. My guess would be that the problem is that, while it's not hard to predict how the moon and sun will influence the earth (i.e. put extra stress on a fault), this would be a matter of regular, periodic increases and decreases. You're surely much more likely to get an earthquake when such an increase changes the stress in a fault from 99.9% of enough to make it shift, to just 100% (made up numbers -- I don't know what proportion of the total this increase would be). But, you need to know first that the stress level is right on the brink of being enough to make an earthquake. You can, then, give a time-accurate prediction for when an earthquake could happen, but without the unobtainable data on exactly where the stress level is, a lot of the time the moon will just make a shift from 92.4% to 92.5% and back (as it were), without having any effect. So, lots of false positives.

Again, just thoughts...

Earthquake catalogues have been searched for correlation with phases of the Moon and none has been found to my knowledge.

Interestingly [to me anyway] a similar search for earthquake triggering by nuclear tests shows a slight [but not statistically significant] correlation that large earthquakes tend to precede underground nuclear tests rather than follow them.

Moonquakes, however, do appear to have a tidal triggering.

Hmmm. That's interesting, but I must say I take the nuclear test thing as a great example of being able to prove anything with statistics. In this case it's not considered significant -- but I read a lot of journals that generally take the .05 level as their definition of significance. That means that, given the number of papers published per issue, the chances are that at least one of them is down to nothing more than random statistical variation....

I've also seen the program where the geologist claimed to predict earthquakes. Intrigued by the throught, I downloaded earthquake records from the USGS for California and then the moon phases from an internet site for the dates where earthquakes were above about 4.5 magnitude. I could not find any statistically significant correlation. Does anyone want to delve deeper? Here's the data...

Moon Phase Earthquake
Year Mn Dy Depth Magnitude
Full 1971 02 09 8.40 6.4 SAN FERNANDO

1/8 waxing 1979 01 01 11.28 5.0 MALIBU '79

1/8 waxing 1986 07 08 10.35 5.6 NORTH PALM SPRINGS

1/4 waxing 1986 07 13 6.00 5.4 OCEANSIDE

Full 1986 07 20 6.00 5.9 CHALFANT VALLEY

Full 1986 07 21 6.00 6.0 CHALFANT VALLEY

Half 1987 10 01 9.53 5.9 WHITTIER NARROWS

1/8 waxing 1987 11 24 4.91 5.9 SUPERSTITION HILLS

1/8 waxing 1987 11 24 2.40 6.1 SUPERSTITION HILLS

1/4 waning 1988 06 10 6.81 5.4 TEJON RANCH

3/4 waxing 1988 06 26 7.89 4.7 UPLAND '88

1/4 waning 1988 12 03 13.34 5.0 PASADENA

Almost Full 1989 01 19 11.86 5.0 MALIBU '89

New Moon 1989 04 07 12.85 4.7 NEWPORT BEACH

Half waxing 1989 06 12 10.78 4.6 MONTEBELLO

1/4 waxing 1990 02 28 5.31 5.4 UPLAND '90

Full waning 1991 06 28 10.53 5.4 SIERRA MADRE

3/4 waning 1992 04 23 12.38 6.1 JOSHUA TREE

New Moon 1992 06 28 1.11 7.3 LANDERS

New Moon 1992 06 28 5.00 6.4 BIG BEAR

1/2 waxing 1993 05 28 21.43 5.2 WHEELER RIDGE

1/4 waxing 1994 01 17 18.20 6.7 NORTHRIDGE

Wouldn't the relevant thing to look at here be tidal phases and magnitudes as correlated with earthquakes?

swyves

ps we're really talking about the moon triggering, rather than causing earthquakes here, aren't we?

Based on what I understood the premise to be, it's the phases of the moon that this guy was correlating to earthquakes, not the tidal phases and magnitudes.

Feel free to delve deeper into this if you want, but there are several things to consider I think. One is the actual gravitational force that the moon has on the earth (I'll see if I can calculate that) compared to the interior stress due to heat convection and flow of molten rock. Another would be to consider that the moon historically been much closer to the earth and is slowly moving away, lessening it's gravitational effects (end result would be that there may have been more frequent earthquakes in geologic history than in the present day...has this been interpreted somewhere?).

Thanks
Canadarocks

I found this web-page interesting as it was debunking the doomsayers that worry about the gravitational effects on Earth when the planets align.

http://drumright.ossm.edu/astronomy/forces.html