Tremors rock earth deep beneath San Andreas Fault - Puzzling vibrations baffle researchers

SF Chronicle ^ | December 10, 2004 | David Perlman

[NYer]

Mysterious tremors deep beneath the San Andreas Fault near the quake-prone town of Parkfield are shaking the earth's brittle crust, far below the region where earthquakes normally strike -- and scientists say they can't understand what's happening or what the motions mean.

Seismic researchers are monitoring the strange vibrations closely. But whether the faint underground tremors -- termed "chatter" by some seismologists -- portend an increased likelihood of a major quake in the area is an unsolved puzzle.

Robert Nadeau, a geophysicist at the UC Berkeley Seismological Laboratory, charted more than 110 of the faint vibrations since they were first detected by the lab's High Resolution Seismic Network in Parkfield three years ago. What concerns Nadeau and his colleagues is that the epicenter of the great 1857 Fort Tejon earthquake, whose magnitude has been estimated at 7.8 to 8, was located almost exactly where the deep tremors are now occurring -- beneath the San Luis Obispo County village of Cholame, some 17 miles south of Parkfield.

The episodes of chatter last from four to 20 minutes and are being recorded from as deep as 40 miles beneath the surface -- up to four times the depth of normal earthquakes, which originate in what scientists call the "seismogenic zone." That zone reaches no deeper than 9 or 10 miles below the Earth's surface.

[NCjim]

"I'm comin Elizabeth, it's the big one!"

[Not A Snowbird]

Similar deep tremors have been detected recently along the coast of the Pacific Northwest, known as the Cascadia Subduction Zone

Uh oh...

[Strategerist]

The episodes of chatter last from four to 20 minutes and are being recorded from as deep as 40 miles beneath the surface -- up to four times the depth of normal earthquakes, which originate in what scientists call the "seismogenic zone." That zone reaches no deeper than 9 or 10 miles below the Earth's surface.

Another bad MSM science article....

The San Andreas is a transform fault and has shallower quakes than subduction zones like Cascadia, West coast of South America, etc. 40 miles is unusual for the San Andreas but not world wide. Deepest quakes are about 400 miles deep.

[Strategerist]

Well, on reviewing the whole article at the link, it's a case of a poorly organized and worded article; they do eventually explain the difference between the San Andreas and subduction faults, and that deep quakes occur on subduction faults, but the opening doesn't make clear the depth of the tremor are unusual for the San Andreas, not for faults world wide.

[Frumious Bandersnatch]

Uh Oh. Sounds like the Terries and the Firmies are up to their old tricks again.

[scott7278]

BM

[Americanwolf]

Hmmmm....... Sounds like me after a bean burrito and sitting in the ocean...

(ok that was sick and wrong, but someone had to do it.)

[upchuck]

Cascadia Subduction Zone

I fooled around with one of those one time. Very kinky. Almost got arrested!!

[GSlob]

Could an earthquake be purposefully triggered by, say, a deep underground nuke in the fault area? If yes, then it could make sense to take a dollar in pennies and to have frequent triggered discharges of accumulated seismic strain so as to get multiple small less destructive earthquakes rather than surprise big ones.

[Smokin' Joe]

Nope. Just Global worming.

[MineralMan]

"Could an earthquake be purposefully triggered by, say, a deep underground nuke in the fault area? If yes, then it could make sense to take a dollar in pennies and to have frequent triggered discharges of accumulated seismic strain so as to get multiple small less destructive earthquakes rather than surprise big ones."

I believe some such thing has been considered. However, I wouldn't want to be in the area when they first tested it. We just don't know enough about these earth movements to start fooling around with nuclear explosions around earthquake faults, IMO.

[MineralMan]

"California is going to be an island. So the song "Ocean Front Property in Arizona" is going to be true!"

That's just ridiculous! Please look at a fault map. The San Andreas is nowhere near Arizona, and the type of fault it is does not lead to that type of destruction.

[nightdriver]

"Uh Oh. Sounds like the Terries and the Firmies are up to their old tricks again."

Some of Walt Disney's more interesting creations. LOL!

Remember which ones wore the bow ties and which ones wore the four-in-hands?

[Jersey Republican Biker Chick]

I wasn't being completely serious. But, my comments are no less silly than those who think it is underground monsters!

[NYer]

*I used to live near there*

Are you still in CA or have you left the state?

I am a native New Yorker. Hurricanes are the biggest natural threat to NY and then, only on Long Island. So it came as a great surprise to me, several years ago, to experience a small quake.

[Frumious Bandersnatch]

No I don't. But I've always loved Carl Barks' illustrations.

[finnman69]

[TommyDale]

"Could an earthquake be purposefully triggered by, say, a deep underground nuke in the fault area?"

I would think that might not be a wise experiment. One of the most devastating earthquakes in recent years was in the small town of Coalinga. The earth dropped, rather than shook, and they think it might have been from pumping so much oil from under the area, causing a cavern.

[TommyDale]

I hate to tell you this, but USGS has found salt water intrusions under the Sierra Nevada Mountains. California is not limited to damage from the San Andreas Fault alone. There are thousands of other fault lines.

[Indie]

(Not to worry, I am in Texas.)

Hope you're not near Caddo Lake...