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.

[ErnBatavia]

there was recent earthquake activity in this area

Uffda! With all the knick-knacks midwesterners have all over their shelves, that could cause some serious breakage!

[Strategerist]

Small (around M3-4) quakes have been triggered by injecting liquid waste in wells, and also by filling large reservoirs after a dam is built.

Both probably are better quake triggers than a nuke.

There's no real way to predict what size quake you get from triggering. Evidence suggests that big quakes are just small quakes that get out of hand.

[IamConservative]

"No worry...It's just another Nancy Pelosi orgasm...."

I hope I can recover from the sudden stomach problems this visual caused in time for Christmas Dinner. Oh no, I just visualized Helen Thomas. Spiraling into the darkness - ewww Hilary visual......................................darkness.

[TC Rider]

Don't worry, if California falls into the sea, we'll just spin the earth backwards and undo it.

[MineralMan]

"Uffda! With all the knick-knacks midwesterners have all over their shelves, that could cause some serious breakage!"

I was talking about my old home in CA. However, the largest historical earthquake in the US happened in the midwest. There's still shaking going on out here, from time to time.

I keep all those knick-knacks on shelves behind glass. Keeps 'em safe, ya know. A guy could do worse.

[sarah_f]

Oh, PLEASE G-d, let it be so! Cuba West.

[Hatteras]

As long as all that monitoring equipment doesn't pick up any deathly screams from the lost souls deep in the bowels of hell we should be okay.

[Old Professer]

One is always surprised at what lurks in the night when one gets a brighter light.

[Ol' Sox]

Must be Gaia, obviously displeased with the election results.

[Thinkin' Gal]

40 miles beneath the surface. That's in the mantle, isn't it? If so, that means possibly hot, squishy rock?

[Churchillspirit]

Your speculation would include Orange County which registered the highest percentage of votes for President Bush in the November election.

Have some compassion for your fellow conservatives who live in earthquake country.

[mewzilla]

Hee hee!! It's a job for Austin Powers!

[OldFriend]

My oops

[blowfish]

Many parts of the East Coast are in *more* danger from earthquake, because they are so infrequent. Most of the big, old fragile buildings on the West coast have been shaken down long ago.
For instance...

[Dog Gone]

they think it might have been from pumping so much oil from under the area, causing a cavern.

That's absurd. Oil isn't an underground lake. It's contained in solid rock.

[Miss Marple]

I am interested in this story, as many moons ago I was a geologist for a coal company. I remember studying about the subduction zones in college, but I am foggy on what quakes at this level could indicate.

My sympathies to the folks in California. Earthquakes are not something I want to deal with...and in central Indiana I insisted that we keep earthquake coverage on our home. We aren't THAT far from the New Madrid Fault.

[vannrox]

"...40 miles beneath the surface..."

This is worrysome.
Sounds like a "dry" fluidic shift.
Could be that this could represent a movement of the magnetic pole.
Let's hope that it's not a pole shift.

[CyberAnt]

Actually, what I find interesting is the map of the pacific rim countries and how the earthquakes have increased around that rim .. just this year alone.

I'm in San Diego. San Andreas is north of me, but another fault (forget the name) rules San Diego. San Andreas could trigger that fault - in which case San Diego would be out in the ocean, or blown to bits when the nuke facility falls apart. ROTFLOL! Either way .. I won't know what hit me.

[PoorMuttly]

Oh. Sorry.

I thought me had gone deep enough.

I be more careful from now on.

Promise.

[TommyDale]

The wells in Monterey County (Salinas Valley) are near the ocean. The Sierra Nevada Mountains are on the other side of the state, running up the Eastern border, some 150 miles away. This appears to be a potential large fracture beneath the shelf currently known as California.