|
. | . |
|
by Staff Writers Paris (AFP) Aug 10, 2014 A monster earthquake that struck Chile in 2010 also unleashed minor "icequakes" in Antarctica nearly 4,700 kilometres (2,900 miles) to the south, scientists said on Sunday. Sensors recorded small tremors in West Antarctica within six hours of the Chilean mega-shock, providing the first evidence that the world's greatest ice sheet can be affected by distant but powerful quakes, they said. Twelve out of 42 monitoring stations dotted across the vast region showed "clear evidence" of a spike in high-frequency seismic signals, the team reported in the journal Nature Geoscience. The signals tallied with signs of ice fractures near the surface, they added. The February 27, 2010 quake, which occurred just off the coast of Chile's Maule region, measured 8.8 in magnitude, making it one of the largest ever recorded. It killed more than 500 people and inflicted an estimated $30 billion (22.5 billion euros) in damages. The main shock from the event triggered micro-quakes as far afield as North America, as the passing shock wave caused shallow faults to slip in tectonically active regions. Geologists have long wondered how the ice sheets in Greenland and Antarctica -- whose underlying rock is considered seismically peaceful -- would respond to gigantic but distant quakes. Until a few years ago, there were no means to explore the idea. But some useful tools have now become available thanks to the deployment of a small network of sensors near and on top of the sheets. The data received after the 2010 earthquake was rather sketchy, the paper said. The clearest signs of activity were detected at a monitoring station in West Antarctica's Ellsworth Mountains, which recorded a telltale seismic signature. But signals received at some of the other stations were unclear or suggested nothing had happened. The best bet is that the tremors came from movement within the ice sheet itself, and not from any fault in the bedrock below, said Zhigang Peng at the Georgia Institute of Technology in Atlanta. "While we are not 100-percent sure, we think that those seismic signals come from ice cracking within the ice sheet, likely very close to the surface," Peng said in an email exchange with AFP. "The main reason is that if those seismic signals were associated with faulting beneath the ice sheet, they would be similar to earthquakes at other tectonically active regions." Put together, the data show that these vast slabs of ice can be sensitive to large, distant quakes, said the paper. But further work will be needed to show how ice sheets respond in greater detail. One intriguing question is the impact on features in the ice sheet -- whether a big distant quake can help to rip open a crevasse or accelerate glacier flow.
Related Links Beyond the Ice Age
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service. |