In the previous post of this series I used a database from National Geophysical Data Center @ NOAA with about 6,000 quakes in it from a couple thousand years ago to our current year.
But I only selected years from 1800 to the present.
I added another set of data that brought the earthquake count up to about 30,000 quakes.
The 6,000 quake set only had the larger quakes, while the later addition contains many small quakes (that even fracking can cause).
That is what I mean by this being puzzling.
Fig. 1 - Fig. 4 follow the hockey-stick pattern, showing few quakes in the past, by comparison to those in more recent times.
The graph of the largest quakes (Fig. 5) shows a different pattern, with the number decreasing in recent times.
My premise was that as melt water from ice sheets in Greenland and Antarctica are relocated to the latitudes nearer to the equator, the change in pressures on fault zones could trigger some quakes (in 'weaker' fault zones).
It could be that fracking is causing a lot of the small ones to show up, but it could also be because of changing pressures due to ice and melt water having been relocated.
I will find more data and continue to build up a robust collection of earthquakes as we move along on this project.
As it is now, I can't say that the hypothesis is falsified or verified.
The increase in quakes in the mainly lower magnitudes is what the hypothesis predicts, but more needs to be done before it can be said to have been verified.
The next post in this series is here, the previous post in this series is here.
Professor McGuire (University College London):