Tectonic Plates Moving Faster: Study September 12, 2014
This aerial view of the San Andreas Fault shows how an untold number of slips have altered the landscape.
Scientists say they have found that Earth’s tectonic plates are now moving faster than at any other point in the last 2 billion years.Plate tectonics is the prevailing geologic process that shapes the planet.
It triggers most of the world’s strongest earthquakes and many volcanic eruptions, along with building mountains and moving continents.
While earlier research seemed to reveal that the massive tectonic plates are actually slowing down as Earth’s core cools, New Mexico Institute of Mining and Technology geochemist Kent Condie and colleagues say they have evidence of faster plate movements.
Writing in the journal Precambrian Research, the team says they looked at how often new mountain belts form when plates collide, and compared it to magnetic data from volcanic rocks.
That allowed them to determine where the rocks formed and how quickly the continents had moved.
At least four faults within the Indo-Australian plate ruptured simultaneously in April 2012, resulting in two magnitude-8 earthquakes within two hours. (Red stars indicate the epicentres.)
Keith Koper, University of Utah Seismograph Stations
Geological stresses rending the Indo-Australian plate apart are likely to have caused the magnitude-8.6 and magnitude-8.2 quakes, which broke along numerous faults and unleashed aftershocks for 6 days afterwards, according to three papers published online today in Nature1–3.
Seismologists have suspected since the 1980s4 that the Indo-Australian plate may be breaking up. But the 11 April earthquakes represent “the most spectacular example” of that process in action, says Matthias Delescluse, a geophysicist at the Ecole Normale Supérieure in Paris and lead author of the first paper1. Worldwide, “it’s the clearest example of newly formed plate boundaries,” he says.
According to prevailing theories of plate tectonics, the Indo-Australian plate began to deform internally about 10 million years ago. As the plate moved northwards, the region near India crunched against the Eurasian plate, thrusting the Himalayas up and slowing India down. Most scientists think that the Australian portion forged ahead, creating twisting tensions that are splitting the plate apart in the Indian Ocean.
Delescluse and his team inferred the presence of these seismic stresses by modelling stress changes from shortly before the 2012 earthquakes. They found that two earlier earthquakes along the eastern plate boundary — the magnitude-9.1 tremor in 2004 that unleashed a massive tsunami across the Indian Ocean, and another quake in 2005 — probably triggered the 2012 event by adding to pent-up stresses in the plate’s middle region.
Gregory Beroza, a seismologist at Stanford University in Palo Alto, California, says that the model is a likely explanation. “The 2004 and 2005 earthquakes by themselves would not have caused this other earthquake. There had to be other stresses,” he says.
Slip-sliding away
Most large earthquakes occur when two plates collide at their boundaries, and one plate slides beneath the other. By contrast, when plates or portions of plates slip horizontally along a fault line, this usually results in smaller, ‘strike-slip’ earthquakes.
However, the first 11 April event defied expectations as the largest strike-slip earthquake on record, and one of the strongest to occur away from any conventional plate boundaries.
In the second study2, researchers found that the accumulated stresses spread over the plate’s interior broke free in the first 11 April event, resulting in one of the most complex fault patterns ever observed. Unlike most earthquakes that shake along a single fault, this one ruptured along four faults, one of which slipped as much as 20–30 metres.
“This earthquake, it was a ‘gee whiz’,” says study author Thorne Lay, a seismologist at the University of California, Santa Cruz.
Previous work had already identified multiple strike-slip faults for the magnitude-8.6 earthquake5, but no other study had analysed the slip amounts in such detail. Beroza says that Lay and his team “do a splendid job of picking apart this very important earthquake” in their paper.
Lasting impressions
Although much attention has focused on how the earthquakes played out, some researchers are also studying the after-effects of the giant tremor. In a third study3, scientists found that for six days following the event, earthquakes of magnitude 5.5 and greater occurred at almost five times their normal rate all around the world.
“Aftershocks are usually restricted to the immediate vicinity of a main shock,” says lead author Fred Pollitz, a geophysicist at the US Geological Survey in Menlo Park, California. He says that the 11 April example should challenge conventional definitions of how soon and how close aftershocks can occur to large earthquakes.
“Every earthquake is important to study, but this earthquake is rather unique,” says Hiroo Kanamori, a seismologist at the California Institute of Technology in Pasadena. With so many unusual characteristics to examine, the 11 April earthquake sequence may continue for some time to expand researchers’ ideas of how earthquakes can occur.
Last 14 days of 5.0M and greater showing the area around the Indo-Australia plate breaking apart:
This explains the West Pacific “unrest” that I’ve been showing in all the earthquake updates for the past year+.
The “spillover” effect is occurring at volcanoes, and adjacent plates to the Indo-Australian plate.. causing an uptick in large earthquakes (compensation for the indo-australian plate demise) around the entire planet… specifically the Pacific ring of fire.
All this activity has lead to the North American Craton, Laurentia, to be ‘moved’ from the WEST.. causing pressure to build upon the N. American craton.. thus, we are seeing activity at ANY spot with deep shaft construction — whether it be dormant volcanoes, fracking/injection well/drilling operations, and even some springs/aquifers ! Not to mention areas having major ‘movement’ problems .. like Bayou Corne, Louisiana — salt dome sinkhole collapse.
It all begins to make sense once you understand OUR plate (north american craton laurentia) is being displaced by the Pacific plate… which itself is being displaced by the Indo-Australian plate breaking apart.
To confirm most of these North American sites are indeed what I say they are… Just look up the coordinates of each greater than 2.5M earthquake in North America via http://earth.google.com to confirm .
