Water extraction for human use boosts California quakes

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Extracting water for human activities is increasing the number of small earthquakes being triggered in California.

A new study suggests that the heavy use of ground water for pumping and irrigation is causing mountains to lift and valleys to subside.

The scientists say this depletion of the water is increasing seismic activity along the San Andreas fault.

They worry that over time this will hasten the occurrence of large quakes.

The report has been published in the journal Nature.

The San Andreas fault runs for almost 1,300km through the western part of California and marks part of the boundary between the Pacific and North American tectonic plates.

Seismologists have mainly focussed on the movements of these plates as the critical factors in the build up of stress that can lead to large earthquakes, such as the one that destroyed San Francisco in 1906.

This paper looks at another factor – the impacts of humans on the Earth's surface.

The researchers have used the well developed GPS system in the western US to analyse small lifts and dips in the topography of the San Joaquin valley.

San Joaquin is part of California's central valley, one of the most productive farm regions in the US. That productivity is based on access to ground water, extracted and pumped to irrigate crops.

So great is the demand that scientists estimate twice as much water is being consumed as is being returned through rain and snow.

All this extraction is having a significant impact on the shape of the Earth. The floors of the valleys are subsiding, the researchers found, while the surrounding mountains are on the rise.

"We are removing a weight from the Earth's crust and it is responding by flexing upwards and literally moving mountains," lead author Dr Colin Amos told BBC News.

Written By: Matt McGrath
continue to source article at bbc.com

4 COMMENTS

  1. It is well known, that water lubricates movement in geological faults, so they are likely to seize up and build up more pressure before breaking, if the smoother lubricated movement is prevented.

    • In reply to #2 by SomersetJohn:

      One wonders if the anti-fracking crowd will add this to their litany of complaints!

      It would take a real idiot to break up rock structures to engage in fracking for methane in an earthquake zone. There are more than enough fires during earthquakes from ruptured gas pipes , without tapping into large natural reservoirs, which being natural, have no shut-off valves!

  2. it’s a wake-up call…

    whisper on a scream :/ A là Twilight Zone episode, no panic until it’s too late, and wars are engaged.

    California, reportedly, will eventually “fall” into the Pacific. Water extraction process, is it expediting the geological shift, as predicted.

    @ 1 – O_o

    @ 2 – err, “complaints”? To quote Dr. Amos again: we need to think more broadly about the impact of our actions in relation to nature.

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