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California's Thirst Triggers Earthquakes, Lifts Mountains


Environment  (tags: california, climate-change, conservation, ecosystems, forests, globalwarming, mountains, water )

Kit
- 1344 days ago - livescience.com
One of California's worst environmental disasters can move mountains and cause earthquakes.



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Comments

Cher C (1430)
Thursday May 15, 2014, 8:42 am


Thnx sweetie!

 

Kit B (276)
Thursday May 15, 2014, 8:45 am
Pin it photo of Half Dome, Yosemite National Park



One of California's worst environmental disasters can move mountains and cause earthquakes.

The Sierra Nevada and other mountain ranges ringing fertile farmlands in California's Central Valley are springing upward atop land freed of an immense weight ó enough water to fill Lake Tahoe.

Thirsty Californians have sucked so much water from beneath the Central Valley that scientists estimate the Sierra Nevada mountains and Coast Ranges both rose nearly 6 inches (15 centimeters) since groundwater pumping started in 1860. The Central Valley grows 25 percent of the nation's food, but most of its water comes from wells, not rainfall.

California's boom-and-bust water cycle not only flexes the Earth, it also triggers earthquakes along the San Andreas Fault, according to the same study, published today (May 14) in the journal Nature. [5 Ways We Waste Water]

"Both the creeping and locked sections of the San Andreas Fault have a seasonal pattern of earthquakes," said lead study author Colin Amos, a geologist at Western Washington University in Bellingham. "The natural signal of the mountains going up and down can explain this pattern."

Heaving Earth

An army of GPS stations reveals mountains surrounding central California's San Joaquin Valley rise and fall each year by the thickness of a dime (1 to 3 millimeters). Here's why: The weight of rain and snow delivered by winter storms pushes down the Earth's crust. In the late summer and fall, the water evaporates and the crust rebounds. Groundwater pumping also peaks in the late summer and fall, boosting the rebound effect.

As the Earth warps, the movement clamps and unclamps the nearby San Andreas Fault, triggering earthquakes, the researchers think.

But donít blame the farmers for earthquakes Ö yet. In the short term, the natural flexing from rain and snow greatly outweighs the changes from groundwater pumping, Amos said.

A similar effect takes place in the Himalayas, which experience far more earthquakes in winter than summer. GPS studies there connected the drenching summer monsoon cycle to changes in the Earth's crust that lead to more winter earthquakes.

The stress on the San Andreas Fault from winter rains, summer evaporation and groundwater pumping is similar in size to the effect of nearby large earthquakes, about 1 kilopascal, the researchers calculated.

However, the study does leave open the possibility that groundwater pumping could give rise to more damaging earthquakes in central California, Amos said. The long-term upward leap from removing so much groundwater is much larger than the seasonal effect. Though it's only a few inches, the 150 years of rebound could bring the San Andreas Fault closer to unleashing another large earthquake, though the study does not say a quake is imminent. Groundwater pumping triggered a deadly magnitude-5.1 earthquake in Lorca, Spain, in 2011.

"This study shows that human-induced changes are significant and must be considered in earthquake hazard analyses," said Paul Lundgren, a geophysicist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, who was not involved in the study.

"The key aspect to keep in mind is that while they can estimate that the unclamping of the San Andreas Fault will promote future seismicity there, they do not know what is the current absolute state of stress on the fault nor how much additional stress accumulation is required to generate the next large earthquake," Lundgren said.

Moving mountains

The findings also neatly solve a long-standing puzzle in California tectonics ó why the southern Sierra Nevadas are springing up so fast. Several explanations have been proposed, mainly focusing on tectonic forces such as faults, but the groundwater link is a better fit, the researchers said.

"We can explain the vertical uplift signal in the Sierra Nevada entirely with groundwater. It doesn't require any tectonic forces at all," Amos said.

JPL researcher Don Argus, an expert on tracking the Sierra Nevada's subtle shifts, also agrees that the groundwater pumping provides a good explanation for the mountain range's steady yearly rise of 1 to 2 millimeters per year. (Thatís about a half inch every 10 years.)

"It was hard to resolve the uplift [with] tectonics in the first place," said Argus, who was not involved in the research. "This is an exciting study."

The Central Valley would be rising, too, if its aquifer weren't missing so much water. Overpumping collapses sediments near the surface, causing subsidence, and California doesn't regulate groundwater pumping. Some towns in the Central Valley are sinking at nearly a foot per year. The Central Valley uses twice as much water as is replenished by rain and snow, and the ongoing drought is prompting farmers to drill even deeper wells.
***

By: Becky Oskin | Live Science |


Becky Oskin was a science reporter at The Pasadena Star-News. She has freelanced for New Scientist and the American Institute of Physics and interned at Discovery News. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what her latest project is, you can follow Becky on Google+.
 

Elizabeth M (65)
Thursday May 15, 2014, 1:44 pm
Noted and shared, with thanks for this very interesting article, Kit.
 

j A (282)
Thursday May 15, 2014, 4:12 pm
All the more reason for a coordinated and responsible water policy emphasizing conservation, storm water capture and recycling. I know and knew too many affected by the last major San Andreas quake.
 

TomCat S (131)
Thursday May 15, 2014, 10:42 pm
It's not only Californicated! It's all fracked up!!
 

Craig Pittman (52)
Friday May 16, 2014, 3:52 am
It does seem to be TomCat. lol Thanks for the read Kit.
 

Past Member (0)
Friday May 16, 2014, 4:17 am
Noted.
 

Camilla Vaga (67)
Friday May 16, 2014, 6:37 am
noted
 

Frances Darcy (170)
Friday May 16, 2014, 7:31 am
Noted Ta Kit...
 

Gloria picchetti (304)
Friday May 16, 2014, 12:46 pm
If you live in California or not we are in trouble!
 

Mitchell D (104)
Friday May 16, 2014, 5:41 pm
Very, very, interesting!
 

Katherine May Williams (0)
Friday May 16, 2014, 6:04 pm
Noted. Wow.
 

Janis K (129)
Friday May 16, 2014, 6:45 pm
Thanks for sharing Kit. Very close to where I live.
 

GGmaSAway D (195)
Friday May 16, 2014, 6:46 pm
More and more we find out how humans are affecting this planet...and the end seems nearer than ever. Scary when mountains move...
 

. (0)
Saturday May 17, 2014, 6:27 am
Very good article Kit. Now factor in the 100 billion barrels of water minimum used in fracking and growing. 90% of that goes back into the earth at 7K'. Now imagine all that water and the 600 or so chemicals it contains under constant, intense pressure and heat as it becomes gaseous. Gas like water will seek the path of least resistance and wherever it can't find one it will create one through resistance to containment in a confined space. In other words it will erode the strata until a channel is created wherein the energy can be released.
The latest study says this has no relevance. Of course many of the same people called me crazy back in 1987 when I tried to tell them there was a direct connection between oil exploration and an increase in earthquakes.
There is a connection which they have now had to admit publicly so they will have to do the same when this chemistry 101 student is proven correct. BTW are they still doing deep sea exploration and carrying out fracking operations in the Pacific? I'll bet you they are.
 

pam w (139)
Saturday May 17, 2014, 7:12 am
it's all about money, isn't it?
 
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