As we begin to enter into solar cycle 24 (which is predicted to peak in early 2013) there has been a lot of discussion about the relationship between
geomagnetic storms and earthquakes. There seems to be a belief that, along with an increase in geomagnetic activity caused by increased solar
activity, we should prepare for an increase in earthquake frequency and magnitude.
I've decided to look for evidence of such a relationship in historical data. For earthquake data I will use the USGS database located here:
For solar and geomagnetic data I will use data which is available here:
. It should be noted that none of the charts I will be using are scaled but it is the shape of the curve rather than
the absolute amplitude which is important.
The first thing I will examine is the frequency of earthquakes as compared to the level of solar activity. I will base solar activity on the annual
sunspot number and I will compare it to the annual number of earthquakes of magnitude 6.5 and greater. Here is a chart representing these two datasets
covering the past three solar cycles.
It can be seen that there is no apparent connection between the 11 year solar cycle and the frequency of earthquakes. But what about the magnitude of
those earthquakes? Here I have plotted the total annual energy (magnitude) of the earthquakes.
It can be seen that the shape of the energy curve is very similar to that of the frequency curve. This indicates that there is a fairly constant ratio
between the number of stronger earthquakes to those of less magnitude. Again we see that there is no apparent connection between the amount of energy
released by earthquakes and the solar cycle.
While sunspot numbers are a good indication of solar activity it may be better to look at something which we know is directly affected by that
activity and which in turn may influence earthquakes, an intermediary so to speak. We know that solar activity can heavily influence the Earth's
magnetosphere, creating fluctuations which we know as geomagnetic storms. Can we find a relationship between these storms and earthquake activity?
The primary method of measuring geomagnetic activity is though the Kp index, a measure of the amount of fluctuation in the Earth's magnetic field.
For this part of the study I will be using a daily Kp index. Since this amounts to a very large amount of data I will limit the study first to an
annual look and then at a smaller scale view. Here I have plotted the daily Kp index and the daily total earthquake energy. For this finer scale data
I have included earthquakes of 4.0 and greater. Here are the plots for 1998 (the beginning of the last solar cycle) and 2001 (the peak).
The first thing we notice is that the data is very noisy. This is something that does make finding correlations difficult. I'm not a statistician and
I don't know how to do Fourier analysis (which might be helpful) but there is no apparent connection between a high Kp index and earthquake activity.
We see several large peaks in Kp index with no unusual earthquake activity at the time or at any particular interval afterward. We see peaks of
earthquake activity with no particular increase in geomagnetic activity.
Now lets try to look closer. I've selected a subset of the data in which there was a fairly high amount of geomagnetic activity over a three month
Again, we see the same thing; peaks of geomagnetic activity with no corresponding change in earthquake activity, peaks of earthquake activity with no
geomagnetic activity to go along with it. We do see some occurrences which seem to have a relationship but there are many more which do not. We see no
relationship between the intensity of geomagnetic activity and earthquake energy. Because of this it cannot be said that there is a relationship
between solar or geomagnetic activity and earthquake frequency and magnitude.
[edit on 4/7/2010 by Phage]