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Many earthquakes are made by humans!

By JW Dowey - 08 Dec 2013 14:59:31 GMT
Many earthquakes are made by humans!

Since ancient times, we have suffered from earthquakes and Etna here, but do we really have to make the earth’s plates move ourselves too? Catania is in the background of the volcano’s maw; Etna image; Credit: © Shutterstock

Earthquakes and vulcanism are natural, created by stresses within the planet and never influenced by mere mortals, or are they? The possibility that we are adding to the terrible loss of life and land in the Ring of Fire or all other earthquake zones feels worse than a horror movie. It is much more than a possibility according to research that is trying to open up the mysteries of earthquake prediction and helping people and countries to save lives and property.

Every nation has experienced the tremors and even the upheavals of earth movement. Frightening though they seem, modern building techniques and useful warnings tend to help people. A catalog of different sizes of earthquake reveals many “geo-engineering” connections to human mining, reservoir construction (imagine the mass of water in a modern Chinese reservoir!), fracking, oil and gas exploration, geothermal energy production and coastal management. They involve mass shifts of the crust from 1kt to a truly massive 1 Tt, similar to the movement, over millions of years, of gravel and other material to a coastal area like Folkestone Harbour, on the English Channel. In 2007, millions of tons accumulating here caused a small 4.3 quake on the Richter Scale in an area which rarely has any tremors.

Stress regimes in different areas can be extensive, transverse or compressive. The magnitude of a quake increases depending on how much mass and over how much area the mass is shifted locally. Random faults do take place independently, but both large and small quakes are connected to these mass shifts particularly when they are so large that they influence the crust more than the regular tidal change. Prime examples may convince any sceptics, so Sichuan in 2008 may serve this purpose. It had a magnitude of 7.9, but most probably linked to the construction (from 2001) of the huge Zipingu reservoir on the Min River. This was very obvious and local event, with the dam walls damaged by the tremor, although the biggest disaster involved the loss of 80, 000 lives.

92 big earthquakes such as this are linked to human interference. Lorca in Spain suffered frighteningly large effects, though few deaths, from a low magnitude 5.1 tremor. The attribution of the quake to local groundwater extraction had been previously made by Dr Pablo Gonzalez. On the other hand, some extensive natural gas extraction caused 3 giant quakes of up to 7.3 on the Richter scale in the Gazli area of Uzbekistan. Central Asia has never experienced seismic activity of such severity, although the capital, Tashkent, was destroyed by an earthquake in 1966.

The lesson seems to be that areas of plate movement are most sensitive to human interference, but that quakes for unprepared populations could be more damaging, even if they are low magnitude. The cataloguer of all of the correlation is Christian Klose, of Think Geohazards and Northwest Research Associates (both in the US), who published these findings in the Journal of Seismology.