SAFOD - San Andreas Fault Observatory at Depth

01101001 · #1 (**permalink**) 05-October-2007, 01:11 AM

We've had some discussion before of SAFOD, San Andreas Fault Observatory at Depth (US Geological Survey), a project that includes drilling into the San Andreas fault in California, between San Francisco and Los Angeles. I located this old (locked) ATM topic: Drilling into the San Andreas fault line, good or moronic? (If you visit that, an inline-graphic from ou.edu will cause you to be asked to log in there; cancel it.)

Today's news: NSF: Geologists Recover Rocks from San Andreas Fault

Quote:

For the first time, geologists have extracted intact rock samples from two miles beneath the surface of the San Andreas Fault, the infamous rupture that runs 800 miles along the length of California.

Never before have so-called "cores" from deep inside an actively moving tectonic boundary been available to study. Now, scientists hope to answer long-standing questions about the fault's composition and properties.

Altogether, the geologists retrieved 135 feet of 4-inch diameter rock cores weighing roughly 1 ton. They were hauled to the surface through a borehole measuring more than 2.5 miles long.
[...]
"To an earthquake scientist, these cores are like the Apollo moon rocks," Hickman said. "Scientists from around the world are anxious to get their hands on them in the hope that they can help solve the mystery of how this major, active plate boundary works."

Nicolas · #2 (**permalink**) 05-October-2007, 08:20 AM

For a moment I thought this SAFOD was something like APOD: San Andreas Fault of the Day. The earth...it's breaking apart! AAAAAAAAAAAAAH!

But ok, it's an observatory.

I'm not too much into geology. These samples should be different from any random place 2 miles down below because these are taken from the very edge of plates?

Fazor · #3 (**permalink**) 05-October-2007, 07:06 PM

These samples should be different from any random place 2 miles down below because these are taken from the very edge of plates?
I don't know, I was sort of wondering that myself. I don't really understand how a core sample of earth, taken out of the interaction which is techtonic motion, will be any different than a core sample of earth from somewhere else...although excluding quantum anything, geology is the science I know the least about.

Re: the claims that drilling on the faul line is dangerious...I don't see how such a relatively small drill would have any major impact on two huge plates. How many thousands of square miles of surface area are in contact along the fault line? And how many inches of that is being disturbed? Come on.

Nicolas · #4 (**permalink**) 08-October-2007, 03:00 PM

Indeed, it's not like they're releasing pressure of a gas bulb there or anything.

Swift · #5 (**permalink**) 08-October-2007, 05:06 PM

Quote:

Originally Posted by Fazor

These samples should be different from any random place 2 miles down below because these are taken from the very edge of plates?
I don't know, I was sort of wondering that myself. I don't really understand how a core sample of earth, taken out of the interaction which is techtonic motion, will be any different than a core sample of earth from somewhere else...although excluding quantum anything, geology is the science I know the least about.

I can imagine several things that might be different (and I'm not a geologist either, but as a solid-state chemist, I'm a distant cousin).

One diffference might be in the exact mineral phases and their proportions. This is going to be dependent upon temperature and pressure. So, even if you have the same chemical composition, the material along the fault may be exposed to different pressure and/or temperatures and have, for example, a different crystal structure.

Similarly, flows of water through the fault could alter the minerals present.

Then, there is this from the NSF story that 01101001 linked to

Quote:

"There have been many theories about why the San Andreas Fault slides along so easily, none of which could be tested directly until now," Hickman said. Some posit the presence of especially slippery clays, called smectites. Others suggest there may be water along the fault plane, lubricating the surface. Still others note the presence of a mineral called serpentine exposed in several places along the surface trace of the fault, which--if it existed at depth--could both weaken the fault and cause it to creep.

If one is going to model earthquakes, one would need to know the exact material the fault is made from, so as to model its mechanical properties.

hhEb09'1 · #6 (**permalink**) 08-October-2007, 05:21 PM

Quote:

Originally Posted by Nicolas

These samples should be different from any random place 2 miles down below because these are taken from the very edge of plates?

Actually, they are most interested in what is going on at the fault itself. The bore has a piece of the contact area, separating two pieces, one from each side of the fault, it appears.

Why does clicking on a BAUT link cause an inline-graphic from ou.edu asking to log in there?

Nicolas · #7 (**permalink**) 08-October-2007, 05:23 PM

Ah ok, now it makes sense to go digging there. Thanks for the info all.

01101001 · #8 (**permalink**) 08-October-2007, 05:32 PM

Quote:

Originally Posted by hhEb09'1

Why does clicking on a BAUT link cause an inline-graphic from ou.edu asking to log in there?

In those articles, Mkingsley inserted an in-line image, hosted at ou.edu, that must have subsequently gone under password protection. Hit cancel. A moderator could zap the image...

From the NSF article, the rocks, right from the fault zone itself, appear to be highly interesting to the rock people. It's 700 feet of fine-grained powder, with serpetine:

Quote:

Might [talc] be smoothing the way for the huge tectonic plates? Chemically, it's possible, for when serpentine is subjected to high temperatures in the presence of water containing silica, it forms talc.

Serpentine might also control how faults behave in other ways. "Serpentine can dissolve in ground water as fault particles grind past each other and then crystallize in nearby open pore spaces, allowing the fault to creep even under very little pressure," Hickman said.
[...]
The only way to know what role serpentine, talc or other minerals play in controlling the behavior of the San Andreas Fault is to study the SAFOD core samples in the laboratory.

01101001 · #9 (**permalink**) 10-July-2008, 02:41 PM

AFP: New technique may help predict quakes

Quote:

Scientists in the United States have devised a method for measuring changes in the speed of seismic waves that could one day help predict earthquakes, a study said Wednesday.

In experiments conducted at the San Andreas Fault Observatory at Depth (SAFOD) in Parkfield, California, Fenglin Niu and colleagues measured the speed of so-called shear waves -- "S-waves" -- before, during and after two small quakes that hit the region in late 2005.

They detected an anomalous signal preceding each of the quakes.

One occurred 10 hours before the temblors hit and the other two hours before, according to the study, published in the British journal Nature.

That would make life interesting if earthquake warnings could be issued hours before the event.

"Party! Got plans for the quake? Come on over to our place. We'll do a barbecue. Bring drinks."

BigDon · #10 (**permalink**) 10-July-2008, 02:55 PM

And we are due for a nice 8 pointer as my oldest was a baby during the last one. We get them every twenty years or so and she was born in '89.

Swift · #11 (**permalink**) 10-July-2008, 02:55 PM

Quote:

Originally Posted by 01101001

That would make life interesting if earthquake warnings could be issued hours before the event.

That would be a major breakthrough.

Quote:

"Party! Got plans for the quake? Come on over to our place. We'll do a barbecue. Bring drinks."

In Louisiana they have hurricane parties and a drink called a Hurricane. Maybe LA needs a drink called an Earthquake?

BigDon · #12 (**permalink**) 10-July-2008, 02:55 PM

011, are you local?

jlhredshift · #13 (**permalink**) 10-July-2008, 03:09 PM

Quote:

Originally Posted by 01101001

AFP: New technique may help predict quakes

That would make life interesting if earthquake warnings could be issued hours before the event.

"Party! Got plans for the quake? Come on over to our place. We'll do a barbecue. Bring drinks."

Uhh.. have a good time, I'll watch from here!

BigDon · #14 (**permalink**) 10-July-2008, 03:30 PM

JL, if you're not inside a building, an earthquake is a big rollercoaster. As we say in San Francisco, earthquakes don't kill people, buildings do.

jlhredshift · #15 (**permalink**) 10-July-2008, 03:54 PM

Quote:

Originally Posted by BigDon

JL, if you're not inside a building, an earthquake is a big rollercoaster. As we say in San Francisco, earthquakes don't kill people, buildings do.

Never thought of it that way, but I'll stay here if you don't mind. I only have to worry about the New Madrid fault, Yellowstone fulfilling its average eruption rate, and a big rock from space, in descending order of probability.

Gillianren · #16 (**permalink**) 10-July-2008, 04:44 PM

Quote:

Originally Posted by jlhredshift

Never thought of it that way, but I'll stay here if you don't mind. I only have to worry about the New Madrid fault, Yellowstone fulfilling its average eruption rate, and a big rock from space, in descending order of probability.

I'd put the big rock above Yellowstone. It's scientifically unsound to build an "average" eruption rate from three eruptions.

BigDon · #17 (**permalink**) 10-July-2008, 07:03 PM

Quote:

Originally Posted by jlhredshift

Never thought of it that way, but I'll stay here if you don't mind. I only have to worry about the New Madrid fault, Yellowstone fulfilling its average eruption rate, and a big rock from space, in descending order of probability.

The apartment I live in is only two stories tall but made with steel I-beam construction. It will take a big shaker to bring it down.

Kaptain K · #18 (**permalink**) 11-July-2008, 02:46 PM

I'll stay here, if you don't mind. Our last volcanic eruption (Pilot Knob) and major earthquake (Balcone's Fault) were both over 60 million years ago. We're far enough from the coast that a hurricane means we get some rain. We're far enough from "tornado Alley" that they are an occasional minor nuisance (unless your one of the rare direct hit victims). We're far enough from Yellowstone that, with the prevailing winds, we shouldn't get more than a light dusting. I guess that leaves "Death from Space_TM to worry about.

jlhredshift · #19 (**permalink**) 11-July-2008, 04:32 PM

Quote:

Originally Posted by Gillianren

I'd put the big rock above Yellowstone. It's scientifically unsound to build an "average" eruption rate from three eruptions.

I'll bet you a one year magazine subscription that Yellowstone happens before the big rock happens (like Thorne-Hawking).