"Slow" Earthquakes May Help Predict Major Quakes

Iphtashu Fitz writes "Think all earthquakes last only seconds or minutes? Think again! Scientists at the University of Washington are measuring a "slow" earthquake some 12 to 25 miles underground that could last as long as a month. Along with the UW scientists, seismologists at the Geological Survey of Canada and Central Washington University have documented at least nine previous so-called slow earthquakes going back to 1992. They seem to occur every 14 months or so, the last one occuring in February and March of last year. These earthquakes, also known as slow-slip earthqakes, can release as much energy as a magnitude 6.8 earthquake but because it's released over such a long period of time nobody on the surface even notices it. One key question the scientists are trying to answer is whether these slow earthquakes add to or relieve stress in the tectonic plates, which could ultimately help to predict major earthqakes."

Comments

can release as much energy

[Visaris]

These earthquakes, also known as slow-slip earthqakes, can release as much energy as a magnitude 6.8

Does this not imply stress is being released?

Re:can release as much energy

[Anonymous Coward]

Stress relief in one place can increase the stress somewhere else. Perhaps that's what they mean. So yes, stress would be relieved by the energy release of the slow-slip earthquake, but this may mean that remaining stresses are now more concentrated somewhere else, which could trigger an ordinary, perhaps dangerous quake.

Re:can release as much energy

[Anonymous Coward]

Another way to put is like this: Imagine a build-up of gas in a stomach. Perhaps a slow release of the gas into the intestinal tract occurs. This does release some energy, but now the stresses in the intestines are increased. Then comes the big fart, and relief ensues. Ahhhh!

Or imagine a river with two reservoirs. The upper one releases energy slowly, filling the lower reservoir, which fills, then reaches bursting point. The energy release at one place does reduce the overall energy potential of the whole system, but increases the local energy of the lower reservoir.

This same effect can occur with ANY quake or energy release, which can lower the overall energy level of the system, but may locally increase stresses somewhere else.

Re:can release as much energy

[TastyWords]

Why would kinetic energy necessarily guarantee a buildup of potential energy?

Think about standing halfway up|down a flight of stairs and you have a package sitting on the stairs and you have it on a rope. Move either way (up or down) on the stairs. Does expending this energy mean a buildup is imminent? Of course not. If you are dragging it down the stairs, as it gets closer & closer to the bottom, the available potential energy is less & less. If you drag the package up the stairs, there is an obvious buildup of energy and if you were to bump the package or accidentally tug on the rope, the energy would be released. And anyone listening (measuring) without seeing the stairs, who would hear the package moving, wouldn't necessarily know which direction it was going - unless|until they learned out to measure a difference in the acoustics.

I'm sure someone's going to shoot holes in this by claiming all sorts of exceptions or places where it doesn't work, but this is just a rough idea.

Re:can release as much energy

[ackthpt]

Does this not imply stress is being released?

The thing is, the plate as massive as it is in scale is elastic and these faults, like the San Andreas may run hundreds of miles. When there's a shift it may only move the whole plate a few inches in an area (or even feet in one example north of San Francisco where a fence was warped) that's a lot of mass to move and we're just standing on it like ants. Some pressure relieved in one locaction undoubtably builds pressure somewhere else, or even transfers presure to a parallel fault. This is a particularly good place to start when looking at the scope of things.

Re:can release as much energy

[cluckshot]

I would suggest that what they are measuring is the train speeding up leaving the station. Then it runs into something...

I recently did some serious looking into the issue of tides etc and found that the trigger event for most earthquakes is a Tidal Flux. Remember there are Land Tides, Atmospheric Tides as well as Ocean Tides. Land Tides are quite significant. The Flux is an interaction between the Sun, Moon and the Earth. Most earthquakes occur when the moon is very close and is at 90, 45, 22.5 degrees etc to the sun. The flux is stronger on the closer to right angles and where the moon/sun aggrigate is accelerating the land. This I would assume is both cause and trigger but it is not fully known.

Other research shows that Full Moons tend to produce more tidal stress than new moons due to Gravity shielding.

There is a lot of research going on regards the prediction of Earthquakes and to represent the most successful to date tech is that like a big board that is being cracked by a hydrolic press, it begins to snap an pop a little then suddenly it fails all together. By listening for the pattern of small pops the big pop becomes more and more certain.

The Tidal techtonic forces have been observed on the moons of Jupiter and Saturn. This is related to the charging up of energy.

UFO type sightings often are precursors to Earthquakes. This is because the earth emits certain sub atomic radiation that appears as solid shiny balls/disks or fast moving ones. This appears to be related to the energy holding the structure of matter together.

I think it's scary...

[Mz6]

Considering that the largest earthquake ever in Washington was a 7.3 in 1874 and that this was largely just discovered a few years ago, perhaps this is a precursor to something big about to happen? More recently was a 1949 earthquake that measured 7.1 near Olympia.

From the Science Daily article..."Making that determination will help in understanding whether they are adding to or relieving stress in the Cascadia subduction zone off the Washington and B.C. coast, where the Juan de Fuca plate dives beneath the North American plate. The subduction zone is capable of generating great earthquakes, and scientists recently determined that a Cascadia earthquake in 1700 measured about 9.0 in magnitude."

And Wired... "The coastal region of northwest Washington state and southeast British Columbia is prone to earthquakes, and scientist warn the area gets hit with a devastating shake of magnitude 9 about every 500 years."

Sure.. we're only 196 years off the 500 year mark since the last 9.0, but for it only to pop up a few years ago makes it seem very ominous.

This data, while very interesting, could still go 2 ways. It is helping to alleviate and prevent major earthquakes in that area, or it's a major precurosr to a huge event that could happen in the near future. The hard part? What is considered teh near future... tomorrow? 5 years? 10 years? Guess we'll have to wait and see.

What's even more interesting is that I have yet to see any reports about this coming from any of the California plates, perhaps it hasn't been found or tested for or it's just not there.. Who knows.

Re:I think it's scary...

[TastyWords]

You want scary?

Here in the midwest (Indiana) we're anxiously awaiting the next quake from the New Madrid fault. The last time it peaked, the Mississippi reversed direction for two days and the ground rippled like waves of four-to-five feet.

Imagine that with the fact most buildings in the midwest, whether it's Chicago, St. Louis, any other city familiar to you - if you aren't familiar with all of the cities, haven't been built to withstand an earthquake. After all, they don't come along often enough to warrant that type of concern and|or expense.

Re:I think it's scary...

[Ann Elk]

And Wired... "The coastal region of northwest Washington state and southeast British Columbia is prone to earthquakes, and scientist warn the area gets hit with a devastating shake of magnitude 9 about every 500 years."

Google for cascadian subduction zone for information on the cause of many of the Pacific Northwest area earthquakes. And yes, the experts predict a huge (>= 9.0) quake in this area Real Soon Now (within a century or two).

Re:I think it's scary...

[happyfrogcow]

Fear! Uncertainty! Doubt! Speculation! Oh My! The world is comming to an end! Maybe we should have a Giant Space Laser that reduces stress in the earth's plates! When will the world end? Today? Tommorow? Yesterday, and this is just the afterlife? ...time for more coffee. Is this a slow news day, or what?

Re:I think it's scary...

[Blakey Rat]

What's really scary is that the local government isn't doing crap about making the city more earthquake safe.

Look at the Alaskan Way Viaduct, for example. An almost identical freeway in California collapsed in the 1989 earthquake. There's been a lot of lip-service about making the viaduct safe, but the only changes I've seen is the installation of a few metal braces on a couple of the supports. That's not good enough!

That viaduct needs to be torn down. If there's any weak point in Seattle's earthquake strategy, that's it.

Re:I think it's scary...

[WhiteBandit]

Also note the 500 year mark is fairly arbitrary in that it is an average.

Down here in Southern California, we've looked at a spot where the San Andreas fault crosses through the Cajon Pass. Digging trenches and things across the fault reveals movement on average every 180 years or so.

The last time that segment of the fault moved was in 1812. 192 years and counting. When you actually plot out when earthquakes occured, you find major events happening as close to 60 years apart to as far away as 220.

So basically, you guys might be due for an earthquake fairly soon... or you might not! ;)

Re:I think it's scary...

[LandGator]

> What's even more interesting is that I have yet
> to see any reports about this coming from any of
> the California plates, perhaps it hasn't been
> found or tested for or it's just not there..
> Who knows.

California's tectonics are significantly different than the OR-WA-BC situation. The Subduction Zone we have up here in the Silicon Forest puts us at much greater risk of The Big One.

An Oregon Department of Geology scientist gave a Tsunami presentation at my Red Cross Disaster Responder meeting earlier this month. She reviewed the history of Tsunamis and the quakes which cause them, at the Oregon shore. Layers of sediment show when there's been a big one. She, and the rest of the department, based on the physical evidence and frequency, think there's one due 'soon'.

Seaside would NOT be a good place to be, ditto for Gold Beach and Florence. If your oceanfront community does NOT have evac routes already plotted, and signage posted, right now, then consider moving.

At very least, go to the ODG website and get the evacuation brochures.

I'm still waiting....

[TastyWords]

...to hear whether piezoelectricity can be used to detect quakes as well. With all of the smashing and crashing going on, one would think it would have the potential to generate radio waves such that a properly tuned instrument could receive|detect the signal.

Re:I'm still waiting....

[gwernol]

...to hear whether piezoelectricity can be used to detect quakes as well. With all of the smashing and crashing going on, one would think it would have the potential to generate radio waves such that a properly tuned instrument could receive|detect the signal.

It usually isn't too difficult to detect earthquakes. Trying to stand up and failing is a perfectly good indicator that (a reasonably large) one is going on :-)

Plus there's seismographs and whatnot that are really pretty good now.

The much more interesting problem is how to predict earthquakes. For this, piezoelectric mechanisms offer no advantage over "conventional" methods.

Re:I'm still waiting....

[GeoGreg]

This sort of thing has been tried without much success so far. There have been intriguing electromagnetic signals recorded over the years (e.g. see this table). However, nobody has been able to come up with a method of prediction using EM that has achieved acceptance among earthquake seismologists. It's much easier to find funny signals after a quake than before.

Re:I'm still waiting....

[WhiteBandit]

Dr. Keilis-Borok at UCLA and his team are claiming to have predicted two earthquakes. One in Japan as well as the one in San Simeon.

Using similiar techniques, they are prediciting an earthquake of a minimum magnitude 6.5 in the Southern California desert by September 5. It will be interesting to see if this pans out.

Interestingly enough, I am have an internship in seisomology with the So. Cal. Earthquake Center this summer and will be working at UCLA. I have a feeling it is going to be quite busy! :)

Politically Incorrect

[Anonymous Coward]

Do *NOT* call them slow...

...they're "special" earthquakes.

:: ducks ::

Re:Politically Incorrect

[geomon]

These kinds of puns are not gneiss. The are just the type of schist that geologists have been objecting to for years.

Re:Politically Incorrect

[Surlyboi]

Isn't that still politically incorrect?

Yeah, but less so than the original term, "Tardquakes".

How come no one

[2names]

ever mentions the fault line that runs along the Mississippi river? Didn't a major quake in the recent past cause the river to run backwards?

Tectonic plates

[Plaeroma]

Can someone explain to me the difference in a 'slow earthquake' and just general plate movement? Cause from I just read, I couldn't differentiate between the two.

Re:Tectonic plates

[geomon]

"Slow" earthquakes are a bit of a misnomer. The energy released in a slow earthquake is the same as the energy released by a catastrophic quake. It is just released over a longer period of time.

General plate movement creates both slow and catastrophic quakes; plate tectonics is the engine driving the stress that creates earthquakes.

You could also add

[geomon]

The seismic staff at the Pacific Northwest National Laboratory

We contribute to the UoW by maintaining the Eastern Washington Seismic Monitoring Network.

add to or relieve stress

[ron_ivi]

"One key question the scientists are trying to answer is whether these slow earthquakes add to or relieve stress in the tectonic plates, which could ultimately help to predict major earthqakes."

Wouldn't it do both. I.e. relieve stress in the spot that slipped, and add to stress in the spots where the plates are still binding?

Re:add to or relieve stress

[geomon]

Yes, the stress relieved at one site may be trasferred to another along the plate margin. But exactly where in the system it is taken up determines whether the "receiving" plate margin will react in a catastrophic manner. Some sites may behave in a plastic (quasi-elastic) fashion and the stress will be dissapated in a slowly developing folded crust. Others will absorb the stress along brittle margins and will eventually react in a non-elastic fault.

More Info Is Always Good

[ackthpt]

The conventional wisdom among my friends and neighbors is, if it has been quiet for too long, it's a bad sign. I've been through a couple 5.0+ earthquakes, the slow rolling type 15-20 seconds and they're pretty nerve wracking, though much preferble to the sudden jolt 3.0+ shockwaves. In Monterey, CA I felt the last 5.4(?) a couple weeks ago down near Paso Robles (probably an aftershock of the 6.5 quake Dec 2003.) As the 2003 illustrates, there are quakes looming in places we're quite unaware until they strike (i.e. Seattle a couple years back), thanks to the complexity of the faults (it's not like there's one fault line, but a who series of fractures along the edge of the plate.) It does seem all the rage of the past few years has been in trying to detect pending quackes along long silent faults, long as in perhaps hundreds or thousands of years.

Still, as far as I have seen the worst to hit North America since europeans settled here struck in a series between 1811 and 1812 near New Madrid, Missouri, one of which reportedly run church bells as far away as Washington DC.

Some day the big one will hit and all the land east of the San Andreas Fault will slide off into the Atlantic Ocean

Re:More Info Is Always Good

[sexylicious]

If you've lived in Seattle, you know that the entire state is a major earthquake zone. I live in Southern California now (lancaster), but I had some fun in the last few major quakes we had there. It's common knowledge up there that the beautiful Cascade Mountains are almost all active volcanos, the rivers flood annually, the windstorms are irritating, and the earthquakes are generally in the range of 3-4.5 if you can feel them.

The geologists up there keep saying that Washington State is due for a huge magnitude quake, something on the order of 8.0. There are also fault lines crisscrossing the Seattle area, Puget Sound, and the outlying areas.

BTW, I read somewhere that a researcher had derived a quake prediction scheme based on seismic data. The scheme has been very accurate so far, but I can't for the life of me remember where I read it. I think it was Scientific American. But the guy predicts a 6.0+ quake in Mojave this fall.

Better article found

[Mz6]

Interview with a USGS official on "slow" quakes back in 1992. Click here!

Possibilities

[Ra5pu7in]

Just some guesses:

A "slow" quake could release stress along a certain section of the plates, but build up pressure along another section further away - thus leading to a large quake along the second section.

A "slow" quake could ramp up to a large quake if the slippage reaches a point where the plates have less friction against each other.

The faults don't only shift when a major earthquake occurs. A "slow" quake may shift the two plates closer to a point that can only shift through a large quake.

Obviously, IANAS or IANAG - and as neither scientist nor geologist - these are mere guesses based on what I do know of earthquakes.

Encourage them!!

[sameerdesai]

I believe a research into predicting earthquakes should be encouraged and given more funding. I am saying this because of my own experience. About 3 years ago, my city and lot of cities around my state experienced a major quake reading 7.8 (Bhuj quake in India) that killed more than 30,000 people. I was sleeping when this happened and it was terrifying. Never in my dream I had imagined my city was in earthquake prone zone. Looking at the rumble and bodies gave me shivers. I believe if such a thing is developed so many lives could be saved (if not property). Also this might help in identifying earthquake zones (if I remeber correctly they classify them in zones based on likelihood of having an earthquake) and that can give an impetus to civil authorities to build earthquake proof houses minimising property damage as well. Just my thoughts.

Predictable Earthquakes

[CharAznable]

I'm from Costa Rica, which has its share of earthquakes. Common wisdom states that the earthquake cycle comes around every 30 to 40 years, and the lasts about 10 years. During that time, a couple of >6.0 earthquakes are expected. This works like clockwork. In 1910, an earthquake levelled the city of Cartago. More high profile earthquakes happened in the 50's, then 30 years of silence, and then the new wave started around 1984 and continued into the early 90's. It now appears to have subsided. In 1991, I experienced the might of a 7.1 quake. I almost crapped my pants.

What did one stress fracture...

[miketo]

...say to the other stress fracture during an earthquake?

"Hey, it's not my fault!"

Re:Give or take? no its Give AND take.

[TastyWords]

look above. that's why I suggested piezoelectricity. Pressure can be exerted upon a rock (even by another rock) and it will generate radio waves. So when you're playing rock, paper, scissors, and the two rocks happen to generate enough pressure, it'd be a matter of trying to know what radio frequencies to know to monitor and get a signal. There are some obvious questions about this - in addition to whether it would work; how broad the frequency spectrum you'd have to monitor, how much lead time you'd get, if the intensity of the impending quake could be measured by the signal, and so on.

I've no idea why...

[Phidoux]

... but this whole Teutonic Plate Movement thing sounds kinda scary and images of blonde hair and blue eyes spring to mind.

Give and Take

[bubba_ry]

One key question the scientists are trying to answer is whether these slow earthquakes add to or relieve stress in the tectonic plates

I am by no means a geologist, but I'd speculate that the slow earthquakes (maybe earthquakes in general?) add stress to some plates and relieve stress in others, somewhat similar to the law of conservation of mass in physical science. That energy has to go somewhere...

Release can add stress

[Kozar_The_Malignant]

This seems counter-intuitive. However, it isn't that far-fetched. Imagine a laterally moving or strike-slip fault (the notorious San Andreas fault is an example). Obviously, motion of the plates on wither side of the fault releases energy. The thing to focus on is what is happening at the ends of the fault. There, the faults can get locked into other plates, and motion causes a build up of stress as motion of one plate is blocked by a stationary plate. Some geologists are concerned that this is happening at the southern end of the San Andreas fault in the San Gorgonio Pass area and at the northern end at the Mendocino Triple Junction.

Why don't they

[millahtime]

Why don't they just call their local psychic. There are even 1-800 numbers for that.

Re:Why don't they

[mark-t]

Why should I have to _call_ a psychic?

If they are really psychic, why don't they call me when they know I need them?

Akamai Mirrors

[karmatic]

Here and Here.

Really Scary

[Kozar_The_Malignant]

I was involved in planning for insurance company response to a quake on the New Madrid fault in the early 90's. Living in California, I'm used to quakes and have lived through some bad ones. A quake on the New Madrid fault would be a monumental disaster on many levels. First, as the writer above points out, the building is not to earthquake standards. Damage would be horrific. Places like Memphis would simple cease to exist.

Second, not only are codes inadequate, but the geology of the area contributes to the problem. The solid parent material (bedrock) allows propagation of the energy over a much wider area than in California. The historic New Madrid quakes cause church bells to ring in Boston. This coupled with the fact that many cities and towns are built on alluvial surface material that undergoes liquifaction during a quake means that once the energy reaches a remote area, it will still do a lot of damage.

Third, the extremely high market penetration of earthquake insurance in the commercial and homeowners insurance markets in the midwest means this would be a world-wide financial disaster far exceeding that of the 9/11/01 World Trade Center loss. Earthquake insurance in most midwest states is dirt cheap and has relatively low deductibles. Everybody has it. Here in California, it is expensive and has very high deductibles. Most people don't have it. If you do the math here, you are better off putting the money you would spend on premiums into mitigation efforts like foundation bolts, masonry reinforcements, etc. Our calculations in the 90's on the dollar loss from a repeat of the New Madrid quakes indicated that a Great Depression style financial collapse was not just possible, but likely.

This is seriously scary shit. The New Madrid Earthquake scare has passed, and not too many people in the midwest are doing any real earthquake planning. The next quake on the New Madrid fault will happen, we just don't know when.

Re:Really Scary

[dgatwood]

I don't think it would be as bad as you think.

So back about 14 years ago, a guy named Iben Browning gave folks a big scare. Even though it never panned out, a lot of older homes were retrofitted during that period, including basic things like tying homes to their foundations, etc.

The state of Tennessee also went through and systematically reengineered many thousands of bridges to make them more earthquake-safe, adding additional ties to ensure that the hooks that hold them in place won't fail if the bridges flop around. They went through and retrofitted all of the buildings on university campuses to comply with strict earthquake codes, including steel cords through all of the bricks in any sufficiently large overhang. I don't think even California's earthquake code is that strict.

Also, a large portion of the weaker buildings, at least in West Tennessee (where the fault in question lies) have been decimated by tornadoes in the past few years, including two devastating hits on Jackson and I believe at least one in Memphis (though I could be remembering wrong). The buildings that resulted from that should meet earthquake code. Mobile homes were designed to be moved, so they shouldn't collapse. That leaves the older homes, most of which have earthquake ties, eliminating the largest cause of damage.

That's not to say that there won't be damage. A nine point will pretty much level anything no matter what you do. Fortunately, that big a quake isn't likely. Odds are in favor of more like a 7 point quake. I wouldn't expect it to be much worse than the equivalent quakes in California---maybe not as bad, since so many older homes and buildings have been brought at least partially up to code.

Re:Found a link

[WhiteBandit]

http://quake.wr.usgs.gov/prepare/factsheets/NewMad rid/

I'm moving.


Personally, I don't know why. I'd much rather deal with earthquakes than tornadoes. In an earthquake, your stuff falls into a nice neat little pile (at least before the ensuing fires engulf it). In a tornado, you, your family and your possesions are blown away into other states. :-P

A great book with the 'big picture' (geologically)

[DieByWire]

John McPhee's 'Annals of the Former World.'

If you're really after the earthquake stuff, just read 'Basin and Range' and 'Assembling California.' (two of the four books that make up 'Annals of the Former World').

In these books, McPhee travels I-80 with a geologist who's an expert in the area they're covering. Each book is about the geology, the geologist, and the road trip. Great read, and you'll end up learning something, whether you intend to or not.