{"314411":{"#nid":"314411","#data":{"type":"news","title":"2010 Chilean earthquake causes icequakes in Antarctica","body":[{"value":"\u003Cp\u003ESeismic events aren\u2019t rare occurrences on Antarctica, where sections of the frozen desert can experience hundreds of micro-earthquakes an hour due to ice deformation. Some scientists call them icequakes. But in March of 2010, the ice sheets in Antarctica vibrated a bit more than usual because of something more than 3,000 miles away: the 8.8-magnitude Chilean earthquake. A new Georgia Institute of Technology study \u003Ca href=\u0022http:\/\/www.nature.com\/ngeo\/journal\/vaop\/ncurrent\/full\/ngeo2212.html\u0022\u003Epublished in Nature Geoscience\u003C\/a\u003E is the first to indicate that Antarctica\u2019s frozen ground is sensitive to seismic waves from distant earthquakes.\u003C\/p\u003E\u003Cp\u003ETo study the quake\u2019s impact on Antarctica, the Georgia Tech team looked at seismic data from 42 stations in the six hours before and after the 3:34 a.m. event. The researchers \u003Ca href=\u0022http:\/\/www.news.gatech.edu\/2012\/02\/22\/listening-90-magnitude-japanese-earthquake\u0022\u003Eused the same technology\u003C\/a\u003E that allowed them to \u201chear\u201d the seismic response at large distances for the devastating 2011 magnitude 9 Japan earthquake as it rumbled through the earth. In other words, they simply removed the longer-period signals as the seismic waves spread from the distant epicenter to identify high-frequency signals from nearby sources. Nearly 30 percent (12 of the 42 stations) showed clear evidence of high-frequency seismic signals as the surface-wave arrived on Antarctica.\u003C\/p\u003E\u003Cp\u003E\u201cWe interpret these events as small icequakes, most of which were triggered during or immediately after the passing of long-period Rayleigh waves generated from the Chilean mainshock,\u201d said Zhigang Peng, an associate professor in the School of Earth and Atmospheric Sciences who led the study. \u201cThis is somewhat different from the micro-earthquakes and tremor caused by both Love and Rayleigh-type surface waves that traditionally occur in other tectonically active regions thousands of miles from large earthquakes.\u003C\/p\u003E\u003Cp\u003EPeng says the subtle difference is that micro-earthquakes respond to both shearing and volumetric deformation from distant events. The newly found icequakes respond only to volumetric deformation.\u003C\/p\u003E\u003Cp\u003E\u201cSuch differences may be subtle, but they tell us that the mechanisms of these triggered icequakes and small earthquakes are different,\u201d Peng added. \u201cOne is more like cracking, while the other is like a shear slip event. It\u2019s similar to two hands passing each other.\u201d\u003C\/p\u003E\u003Cp\u003ESome of the icequakes were quick bursts and over in less than one second. Others were long duration, tremor-like signals up to 10 seconds. They occurred in various parts of the continent, including seismic stations along the coast and near the South Pole.\u003C\/p\u003E\u003Cp\u003EThe researchers found the clearest indication of induced high-frequency signals at station HOWD near the northwest corner of the Ellsworth Mountains. Short bursts occurred when the P wave hit the station, then continued again when the Rayleigh wave arrived. The triggered icequakes had very similar high waveform patterns, which indicates repeated failure at a single location, possibly by the opening of cracks.\u003C\/p\u003E\u003Cp\u003EPeng says the source locations of the icequakes are difficult to determine because there isn\u2019t an extensive seismic network coverage in Antarctica.\u003C\/p\u003E\u003Cp\u003E\u201cBut at least some of the icequakes themselves create surface waves, so they are probably formed very close to the ice surface,\u201d he added. \u201cWhile we cannot be certain, we suspect they simply reflect fracturing of ice in the near surface due to alternating volumetric compressions and expansions as the Rayleigh waves passed through Antarctica\u2019s frozen ice.\u201d\u003C\/p\u003E\u003Cp\u003EAntarctica was originally not on the research team\u2019s target list. While examining seismic stations in the Southern Hemisphere, Peng \u201caccidently\u201d found the triggered icequakes at a few openly available stations. He and former Georgia Tech postdoctoral student Jake Walter (now a research scientist at the Institute for Geophysics at UT Austin) then reached out to other seismologists (the paper\u2019s four co-authors) who\u0026nbsp;were in charge of deploying more broadband seismometers in Antarctica.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EThis project is partially supported by a National Science Foundation CAREER grant (EAR-0956051). \u003Cem\u003EAny conclusions expressed are those of the principal investigator and may not necessarily represent the official views of the NSF.\u003C\/em\u003E\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Technology allows scientists to hear seismic waves as they arrived on frozen continent"}],"field_summary":[{"value":"\u003Cp\u003ESeismic events aren\u2019t rare occurrences on Antarctica, where sections of the frozen desert can experience hundreds of micro-earthquakes an hour due to ice deformation. Some scientists call them icequakes. But in March of 2010, the ice sheets in Antarctica vibrated a bit more than usual because of something more than 3,000 miles away: the 8.8-magnitude Chilean earthquake. A new Georgia Institute of Technology study published in Nature Geoscience is the first to indicate that Antarctica\u2019s frozen ground is sensitive to seismic waves from distant earthquakes.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Study is the first to indicate that Antarctica is sensitive to seismic waves from distant earthquakes"}],"uid":"27560","created_gmt":"2014-08-11 09:00:19","changed_gmt":"2016-10-08 03:16:52","author":"Jason Maderer","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2014-08-11T00:00:00-04:00","iso_date":"2014-08-11T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"314361":{"id":"314361","type":"image","title":"HOWD Seismic Station","body":null,"created":"1449244929","gmt_created":"2015-12-04 16:02:09","changed":"1475895022","gmt_changed":"2016-10-08 02:50:22","alt":"HOWD Seismic Station","file":{"fid":"199907","name":"erickendrick_touched_up066.jpg","image_path":"\/sites\/default\/files\/images\/erickendrick_touched_up066_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/erickendrick_touched_up066_0.jpg","mime":"image\/jpeg","size":1741740,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/erickendrick_touched_up066_0.jpg?itok=ZZwf9Ave"}},"314351":{"id":"314351","type":"image","title":"Ellsworth Mountains","body":null,"created":"1449244929","gmt_created":"2015-12-04 16:02:09","changed":"1475895022","gmt_changed":"2016-10-08 02:50:22","alt":"Ellsworth Mountains","file":{"fid":"199906","name":"jameystutz_howd.jpg","image_path":"\/sites\/default\/files\/images\/jameystutz_howd_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/jameystutz_howd_0.jpg","mime":"image\/jpeg","size":4729249,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/jameystutz_howd_0.jpg?itok=-GHNGBpe"}}},"media_ids":["314361","314351"],"related_links":[{"url":"http:\/\/www.cos.gatech.edu\/","title":"College of Sciences"},{"url":"http:\/\/www.nature.com\/ngeo\/journal\/vaop\/ncurrent\/full\/ngeo2212.html","title":"Nature Geoscience Paper"},{"url":"http:\/\/www.eas.gatech.edu\/","title":"School of Earth and Atmospheric Sciences"}],"groups":[{"id":"1183","name":"Home"}],"categories":[],"keywords":[{"id":"479","name":"Green Buzz"},{"id":"99311","name":"Icequakes"},{"id":"12122","name":"Zhigang Peng"}],"core_research_areas":[{"id":"39431","name":"Data Engineering and Science"},{"id":"39531","name":"Energy and Sustainable Infrastructure"}],"news_room_topics":[{"id":"71911","name":"Earth and Environment"},{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJason Maderer\u003Cbr \/\u003ENational Media Relations\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-385-2966\u003C\/p\u003E","format":"limited_html"}],"email":["maderer@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}