Where the Fault Lies within a Plate
Major faults occur at the point where two tectonic plates collide. But they can also exist within plates, as the New Madrid fault does in the middle of North America. Scientists are still unsure what powers these intraplate earthquakes; they may result from some combination of forces, such as the removal of glacial sheets after the last ice age or the drag from the fluid mantle underneath the plates. Earthquakes from such faults can be quite powerful and deadly. “Perhaps the most damaging earthquake in Australia’s recent history was in Newcastle in 1989, when a quake measuring 5.6 killed 13 people and left a damage bill of billions of dollars. It was in the middle of the continent,” recounts Seth Stein of Northwestern University. China and northern Europe may also be good places to investigate such activity.
Note: This article was originally printed with the title, "Rumble Off".
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8 Comments
Add CommentThough I am not scientifically trained, I have lived in both California and Indiana and been present when a quakes occured. As a civilian, the difference that I've noticed is that the California quakes (ie 1971 quake, 6+) felt like one was sitting on a table and people were pulling/pushing the legs in several different directions as once...thus kind of a bucking effect. The quake we just had in Indiana early this spring was more like a rolling effect, like a billowing sheet. It was much more gentle (5.1).
Reply | Report Abuse | Link to thisThe article was interesting, thank you.
an apparent cycle of 500 years is sampled for 8 years and a conclusion is drawn? This is SCIENCE???
Reply | Report Abuse | Link to thisPlease!
I agree that 8 years of data may not be valid to draw conclusions about the status of phenomenon with a period of 500 years. We thought the N Atlantic meridional overturning circulation was shutting down, then new data suggested that it has a high degree of variability with a period of variation significant longer than the original data set. Also, the conclusion about the New Madrid system shutting down is based on the plate tectonics model, where slippage at subduction or transform boundaries provides the elastic energy released in large earthquakes. An alternative hypothesis to declaring a shutdown of a process that has repeated at least 3 times over millenia is that we don't understand the mechanisms that cause intraplate earthquakes. Classic plate tectonics may not fit every earthquake. Certainly there is no lack of seismic activity in the New Madrid zone. It has been suggested that seismic pumping of fluids out of the New Madrid zone was responsible for at least part of the Tri-State lead-zinc deposits. These deposits are late Permian to early Mezozoic, so, declaring a 'shutdown' may be a little premature. However, the result of no detectable surface deformation over 8 years is a very significant finding and a very interesting piece of data.
Reply | Report Abuse | Link to thisThe research data seems to show little LATERIAL movement.
Reply | Report Abuse | Link to thisIf i remember correctly the New Madrid fault movement is primarly vertical and that there is a sometimes mountain range just to the south sometimes it's up and presently it's down. Not to worry! it's at least 250 years to the next movement.
Something i've never heard mentioned but seems logical is the upheavals that would occur earthwide from a massive melting of glacial and polar ice- would seem to me that the natural path for much of that water would be the equator, seeing that it already bulges from centrifugal force of Earth's rotation. This would speed the spin of Earth as well. Whatever the case, there is no doubt that you could not shift that much weight around the Earth and not create mechanical imbalances in Earth's crust that are only corrected with an earthquake. I can foresee such a cascade of events helping to fulfill Christ' prophecy that there will be great earthquakes in one place after another before 'the end' comes.
Reply | Report Abuse | Link to thisHas anyone tried doing a stress analysis of the North American plate using something like NASTRAN? Is the New Madrid fault zone the result of a stress concentration in the middle of the plate?
Reply | Report Abuse | Link to this@PsySciGuy
Reply | Report Abuse | Link to thisThey measured ground deformation on sub-millimetre scales over 8 years; the 500 year cycle refers to major earthquakes. Although related, they are different phenomena. It is science and they do actually know what they're talking about.
I would love to know which is actually the larger fault, the SanAdreas or New Madrid fault, could someone please give me an answer
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