Andrew Somervell

Ground water earthquakes

14 April 2011

For years I’ve heard farmers on the Canterbury plains bemoan the dropping water table. Each one explaining water bores — that give life to their fields — never needed to be more than 30m deep. Now, they need to be at least 150m. Let that… sink in… for a minute!

It’s New Zealand’s largest region by area, 45,346 km2. Times 120m of ground water is… A shit tonne of water. I’ll come up with a Scientific Wild Assed Guess (SWAG) estimate how much water soon. It’ll be some function of the porosity of the prevailing ground. Something like this.

And we know a shit tonne of water an equal shit tonne of weight.

So what would happen then, if the earth’s crust was relieved of all that weight?

With all the movement in young New Zealand, would such a significant weight change make an impact on the upper layer of land, and a new fault? Or faults!?

Do humans removing lets say 20% of the volume of the ground under them, cause themselves grief?

I reckon it begs the question, “did farming in Canterbury cause so much change to the dynamic of the region that a new fault appeared, and caused all that fuss???”

Or put scientifically, our null hypothesis is: “Removing groundwater from beneath a region causes no significant change in seismic activity.” What would it take to disprove it?