California's Central Valley Earthquakes, Ground Water Depletion, and The Big One

A couple of observations from two articles that talk about the depletion of ground water and earthquakes.

Small EQs
Depletion of Central Valley's groundwater may be causing earthquakes

Groundwater is very heavy, and its weight depresses the Earth's upper crust. Remove the weight, and the crust springs upward — and that change in pressure can trigger more small earthquakes, the researchers said

"It reduces the forces that are keeping the fault clamped together — leading to more small earthquakes during dry periods of time," said Colin B. Amos, assistant professor of geology at Western Washington University, the study's lead author.

The recent mini swarm near Kettleman City may help their case. Could we expect more as summer continues?

My Observation:
While there is not many structures for an EQ to damage in the valley, there is the California Aqueduct that parallels Highway 5 and was very close to a couple of 3.0's this week near Kettleman City. There's a lot of water pumping through there going over to Los Angels. That would be some displacement of water if the walls of that aqueduct failed.

Big One?
Sierra rises, quakes erupt as Central Valley aquifer drained

The pace of uplift in the Sierra is measured only in millimeters, but when California experienced bone-dry seasons between 2003 and 2010 and pumping increased up and down the Central Valley, the High Sierra rose by about 10 millimeters, the geophysicists say. That's nearly half an inch during those seven years alone.

"The periodic stress on earthquake faults would be very small, but in some circumstances even such small stress changes can be the straw that breaks the camel's back," Bürgmann said. "The stresses from the rebounding mountains would give just that extra force needed to unclamp the (San Andreas) fault and encourage, not only small earthquakes, but also larger ruptures to occur."

So should our EQ watchers out there start focusing on CA during the summer.

My Observations:
There seems to be more activity on the valley floor recently I'm presuming it is from what the articles above describe as depleting of the ground water. If this drought cycle continues I would also presume that the odds increase of a bigger EQ being triggered by all that movement.

Discussion.
Do you think the science behind ground water depletion causing EQs is solid? Should California be we worried?
If a big one hits could the farmers be held responsible?

Thanks for reading.

a reply to: Observationalist

I would be thinking along those lines but more importantly, water in aquifers disappearing lower into the earth through earthquake fractures could cause some huge problems. If the water drops deep enough into the crust and fast enough, the water could convert to steam. Steam expands rapidly and if contained can cause explosive pressure. Obviously it would have to drop miles into the crust, but anything is possible.

The earth's crust is apparently about 3 to 30 miles thick and once you get down to the mantle you'd be looking at a temperature of about 1800 degrees F. So, let's assume fairly uniform thermal transfer (even though it is a bit non-linear) and use a surface temperature of 32 F (water still liquid) and an average crust thickness of say 20 miles, the linear expression of temperature of the crust would be about 88.5 degrees F per mile depth. So, 3 miles down (~265F), water could be converted to steam, 5 miles down (~440F) quite easily and at 10 miles down (~900F) it would flash into steam and the pressure created could be explosive and enough to move some geological features (and act as a lubricator/facilitator).

Just some thoughts.

ETA: This is one of the really dangerous things about fracking. They break apart underground structures to get fossil fuels, but the water and other junk they put down there can create underground fires, explosions and of course the water/junk can move lower in the crust opening up a whole series of new and improved problems.

Cheers - Dave

I think it is a viable theory. It is just a theory though. It isn't going to apply to all types of movement, it will have parameters that need to be considered.

a reply to: Observationalist

Great post - thanks. Geophysical stability results from a balancing of multiple factors, and it's not something we should take for granted. Your info adds an important dimension. ...I think the stuff in our earth (water, oil, gas) acts as shock absorbers - remove them and you have a big problem.


F&S&

Ok ,
So I've lived in the central valley most of my life and might be able to illuminate the subject a little.
I've read the paper from the OP, and they are making extremly generalized assumptions.
First off one needs to understand the geology of this area. Lets start with the eastern side of things.
The sierra Nevada are one of the oldest mountain ranges in the world, over 200,000,000 yo, and they are being eroded faster than they are being pushed up. The major rivers, the Kern, Kings and San Joaquin have been here since before the mountains started to raise, as their canyons cut completely through the range. One of the mechanisms pushing them up is the rifting of north America further east, this failed rift is pushing everything west of the Mississippi, west. At the same time the former island arc that is the coast range is moving north along the boundy of the pacific plate and north American plate. This is pushing up the sierra, now.
To be continued

a reply to: punkinworks10
So as the island arc pushed up against the NA plate it closed up an inland sea. This former inland sea is what we now call the central valley. It is filled nearly 10,000' deep with sediments from the sierra. So the central valley is essentially a big bowl of sand.
The aquifer here can be very shallow and very deep at the same time, where I'm at right now m minimum water table is about 150' down, but the farther west you go the deepe it gets there arevwells on the west side of the valley that are 2500'-3000' deep.
Now I'm some what skeptical of the paper in the OP
As to micro quakes near kettleman city, there have always been lots of quakes there, it's inlyva few miles from parkfield , which is the most siesmically active area in the US, so it's not surprising to see micro quakes at kettleman. It's also been shown that in years of heavy rain fall along the San Andreas, which is in a usually very arid place, you get more small surface quakes.
As to the sierra going up that much in ten years, what about the previous century of pumping ground water. Or the fact that Mnt. San Jacinto, in the San Gabrials, (so cal) went up almost a foot during s large quake in the nineties.
I don't think the drop in the water table is responsible for increased uplift of the serra, but since we have had less tha average rainfall for a couple of years, the lakes of the Sierra ate all nearly empty. That loss of weight should cause isostatic rebound, as the weight of all od those lakes lies directly on the sierrra.
Unless you live in the area and have gotten off of the beaten path you would never realize how many lakes there are and how big some of them are .
There are going to be more than one "big one" in California, and they are not really going to be related to anything humans are doing. Also there is plenty for earthquakes to damage in the central valley , it is home to several million people and has a Greta deal of industry, especially in food proccesing and agricultural industry.
But , there isn't much to fear , since as I mentioned the valley is a big bowl of sand, and seismic waves don't propogate through the medium very well.

a reply to: bobs_uruncle

Interesting scenario, I think we might underestimate the power of water, its weight, movement and erosive qualities. We can observe it above ground and prepare accordingly but not so much in the subterranean reaches of the earth.

To me its not just the displacement of water from one place the next it's what it does on its way.