Part I: The Moon
This is getting a bit old. Time and time again, someone bops along with the idea that the Moon or the sun causes an increase in seismicity. They climb up on their soapbox and thump their chest denouncing the world (that would be the rest of us) are blind to the obvious correlation. That we will all suffer ruination if we don’t heed their warnings or suffers some calamity akin to a slow and brutal death.
Hey, sounds like fun. Let’s play.
Here is a plot of all earthquakes greater than Magnitude 4.5 as listed on the USGS website from 1973 to 2010.
Wow, that look a bit compelling. How about the power distribution across that same data?
Well… that seals the deal. Right?
Not so fast.
First, I would like to point out that there is some research that points to a lunar influence in the activity of certain already seismically active regions, but that this research is founded on actual science. The effect is ephemeral and buried in noise. This is not intended to debunk that research, only to illustrate just how misleading some of the source data is, and how easy it is to jump to conclusions.
Now here is the nugget-o-truth that most people tend to miss:
The longer that the Moon spends at a specific location, the more likely it is that quakes will occur while it is at that location.
The Moon completes an orbit around the Earth about every 27.321 days. All orbits have a Perapsis (closest point on orbit) and an Apoapsis (furthest point). At perapsis the Moon is at it’s highest rate of speed at about 1.076 km/s.1 At apoapsis, it is moving at 0.964 km/s1. Obviously, this speed is not constant. The period of the Lunar orbit is 27.321582 days2 . The Moon goes through a full phase cycle in about 29.53 days3. That’s almost the same period… but it’s not. Couple this with the dynamics of an elliptical orbit, and you get this odd characteristic.
This is the dwell time of the Moon on two separate phase cycles. Notice that the curves, though similar, do not match. This is due to the ‘not quite the same’ durations of the phase cycle and the orbital period. Also notice that the amount of time spent at the New and Full phases is longer than at mid phase.
Let’s take a look at several cycles in order to see if there is a pattern.
Sure enough… that orange is the plot of several phase cycles. The blue is an average of what is seen at that phase over those same cycles. (the average of the orange curve). We can go a step further and run this through a curve fitting program in order to see if there is a function that matches.
That’s pretty good… but note the end points, even though the curve is a good fit, it leave enough uncertainty on the ends to make it mostly useless. I provided the plot mainly since I pissed away about two and a half hours in Erueqa’s “Formulize” in order to find it. (it’s a really great program though).
Taking the idea of using the mean of the curve to calculate a correction factor, and using the 1000 bin average from the previous plot (the one with the orange and blue), we can apply that to the quake count curve.
Err… where did the trends go? Okay, maybe the power curve will still show the significant signal.
Hmm… not looking so good.
There is still an artifact in there… at least it seems to me like there is an artifact in there… but it’s small. So small that the last thing I would do would be to stand on a soap box preaching at people about it.
Part II: The Sun and the Moon
I realize that some people are adamant about the seismic connection with the Sun and the Moon. I also realize that I have pointed out a few issues with making this connection. One might argue that I was being very selective in presenting the data… okay, fair enough.
Here are some more plots that may, or may not, show a connection. You be the judge.
Nothing there that really jumps out at ya eh? Okay, a few more:
Do note that the apparent dwell time of the Sun at mid Winter and Mid Summer really stands out in that last plot. By the way, see those horizontal bands? Those are the latitudes of seismically active areas.
Again, the bands equate to known active areas… this time in longitude.
You may think me an ass for not believing in the Sun-Moon-Earth connection. That’s your prerogative. But unlike some, I actually went out and looked for myself. I’m not one to buy a pig in a poke. Personally, I don’t see it in the data. If your numeric skills are better, knock yourself out. I could stand to learn a thing or two while reading it. But if it’s BS, I’m not gonna buy it.