New Madrid fault system may be shutting down
March 13, 2009 By Elizabeth K. Gardner
Earthquake damage, Dec. 16, 1811.
(PhysOrg.com) -- The New Madrid fault system does not behave as earthquake hazard models assume and may be in the process of shutting down, a new study shows.
A team from Purdue and Northwestern universities analyzed the fault motion for eight years using global positioning system measurements and found that it is much less than expected given the 500- to 1,000-year repeat cycle for major earthquakes on that fault. The last large earthquakes in the New Madrid seismic zone were magnitude 7-7.5 events in 1811 and 1812.
Estimating an accurate earthquake threat for the area, which includes parts of Illinois, Indiana, Tennessee, Arkansas and Kentucky, is crucial for the communities potentially affected, said Eric Calais, the Purdue researcher who led the study.
"Our findings suggest the steady-state model of quasi-cyclical earthquakes that works well for faults at the boundaries of tectonic plates, such as the San Andreas fault, does not apply to the New Madrid fault," said Calais, who is a professor of earth and atmospheric sciences. "At plate boundaries, faults move at a rate that is consistent with the rate of earthquakes so that past events are a reliable guide to the future. In continents, this does not work. The past is not necessarily a key to the future, which makes estimating earthquake hazard particularly difficult."
The team determined that the ground surrounding the fault system is moving at a rate of less than 0.2 millimeters per year and there is likely no motion. A paper detailing the work is published in the current issue of Science magazine.
Seth Stein, co-author of the paper, said this surface movement represents energy being stored that could be released as an earthquake.
"Building up energy for an earthquake is like saving money for a big purchase," said Stein, the William Deering Professor of Earth and Planetary Sciences at Northwestern University. "You put money in over a long period of time and then spend it all at once and have to start saving again."
With an earthquake, it is elastic deformation that must be built up. This can be measured using GPS through movements on the surface, he said.
"The slower the ground moves, the longer it takes until the next earthquake, and if it stops moving, the fault could be shutting down," Stein said. "We can't tell whether the recent cluster of big earthquakes in the New Madrid is coming to an end. But the longer the GPS data keep showing no motion, the more likely it seems."
The U.S. Geological Survey-funded study used data recorded at nine GPS antennas mounted in the ground in the earthquake zone.
"GPS technology can measure movement to the thickness of a fishing line," Stein said. "Use of GPS to study earthquakes shows the impact a new technology can have. It lets us see that the world is different than we thought it was."
In the Midwest there are other faults that show no activity today but have evidence of earthquakes occurring within the past 10,000 to 1 million years, Calais said.
"If other faults in the central and eastern U.S. have been active recently, geologically speaking, they could potentially be activated again in the future," he said. "We need to develop a new paradigm for how earthquakes happen at faults that are inside continents."
Calais and Stein are exploring possible explanations for the behavior of faults like the New Madrid. One possibility is that earthquakes in these areas occur in clusters and then migrate to a nearby fault.
"There is the possibility that seismicity migrates with time as earthquakes trigger earthquakes on nearby faults," Calais said. "Geologists studying the seismic history of faults have found that there have been earthquakes on several faults in the central and eastern U.S. and that they seem to produce bursts of earthquakes and then turn off."
The team is doing additional analysis and modeling to study this further.
More information: Time-Variable Deformation in the New Madrid Seismic Zone, E. Calais and S. Stein, Science.
-
Earthquake in Illinois could portend an emerging threat
Apr 24, 2008 |
not rated yet |
0
-
Geologists study China earthquake for glimpse into future
Jul 06, 2008 |
not rated yet |
0
-
Experts disagree about earthquake risk
Dec 15, 2005 |
not rated yet |
0
-
Ill. earthquake a wake-up call
Apr 20, 2008 |
not rated yet |
0
-
Caribbean Earthquake Model
Dec 22, 2006 |
not rated yet |
0
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (31) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (3) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (1) |
0
-
Discrepancy between oxygen and carbon-dioxide levels
Feb 09, 2012
-
where gems are found in the world
Feb 09, 2012
-
Wind Waves in Reservoir ~ Wind run-up and Wind set-up
Feb 08, 2012
-
Balance of oxygen in the atmosphere
Feb 01, 2012
-
The case for a methanol-based economy
Jan 30, 2012
-
Weather in a rotating cylinder
Jan 25, 2012
- More from Physics Forums - Earth
More news stories
Humans may have helped the decline of African rainforests 3000 years ago
(PhysOrg.com) -- Large areas of rainforests in Central Africa mysteriously disappeared over three thousand years ago, to be replaced by savannas. The prevailing theory has been that the cause was a change ...
Could Venus be shifting gear?
(PhysOrg.com) -- ESAs Venus Express spacecraft has discovered that our cloud-covered neighbour spins a little slower than previously measured. Peering through the dense atmosphere in the infrared, the ...
Space & Earth / Space Exploration
18 hours ago |
5 / 5 (7) |
8
|
NASA budget will axe Mars deal with Europe: scientists
US President Barack Obama's budget proposal to be submitted next week for 2013 will cut NASA's budget by 20 percent and eliminate a major partnership with Europe on Mars exploration, scientists said Thursday.
Space & Earth / Space Exploration
21 hours ago |
5 / 5 (2) |
18
Two new moons for Jupiter
Advances in technology have lead to the discovery of new planets outside of our Solar System, and now even new moons in our own backyard.
Space & Earth / Space Exploration
18 hours ago |
4 / 5 (1) |
7
Mars Science Laboratory computer issue resolved
(PhysOrg.com) -- Engineers have found the root cause of a computer reset that occurred two months ago on NASA's Mars Science Laboratory and have determined how to correct it.
Space & Earth / Space Exploration
19 hours ago |
4.7 / 5 (6) |
3
|
Anonymous knocks CIA website offline (Update)
The website of the Central Intelligence Agency was inaccessible on Friday after the hacker group Anonymous claimed to have knocked it offline.
New error-correcting codes guarantee the fastest possible rate of data transmission
Error-correcting codes are one of the triumphs of the digital age. Theyre a way of encoding information so that it can be transmitted across a communication channel such as an optical fiber o ...
Google users warned of threat to smartphone wallets
Users of Google smartphone wallets were being warned on Friday that there is a way to crack pass codes intended to thwart thieves from going on illicit shopping sprees.
New power source discovered
(PhysOrg.com) -- Researchers at the Massachusetts Institute of Technology (MIT) and RMIT University have made a breakthrough in energy storage and power generation.
Small modular reactor design could be a 'SUPERSTAR'
(PhysOrg.com) -- Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor ...
The power of estrogen -- male snakes attract other males
A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and turned the males into just about the sexiest ...
Mar 13, 2009
Rank: 5 / 5 (3)
Mar 13, 2009
Rank: 4.7 / 5 (3)
The crust is not entirely rigid... A chunk of the crust can be flexed a bit before the stress is released and an earthquake occurs. What they are saying is that they see no movement (flexing) of the crust surrounding the faults. No movement means that there is no significant stress building up at this time.
Note: this does not preclude the possibility that stress has already built up, and is simply being held in tension, without increasing or decreasing, but I suspect that this would be fairly unlikely, and at least some movement would be noted.
Mar 13, 2009
Rank: 5 / 5 (3)
Mar 14, 2009
Rank: 5 / 5 (3)
Mar 15, 2009
Rank: 3 / 5 (2)