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"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."
The seismic staff at the Pacific Northwest National Laboratory
We contribute to the UoW by maintaining the Eastern Washington Seismic Monitoring Network.
"Rocky Rococo, at your cervix!"
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
A feeling of having made the same mistake before: Deja Foobar
Interview with a USGS official on "slow" quakes back in 1992. Click here!
Hmmm.
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).
"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.
"Rocky Rococo, at your cervix!"
Yes, he predicted one on Tokyo.. it happened like 2 days after his predicted date.. so it needs more work but it was close.. there was a show on tv a year ago about predicting earthquakes.. i forget what they were doing but they had maps of where possible earthquakes would happen.. and he predicted like several major earthquakes.. but he couldnt help anyone because if he said "you're going to have an earthquake on BLAH".. no one would believe him
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.
The perfect sig is a lot like silence, only louder
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.
A feeling of having made the same mistake before: Deja Foobar
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.
Some mornings it's hardly worth chewing through the restraints to get out of bed.
Here and Here.
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.
Some mornings it's hardly worth chewing through the restraints to get out of bed.
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.
http://quake.wr.usgs.gov/prepare/factsheets/NewMa
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.
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.
Never shake hands with a man you meet in a fertility clinic.