New research demonstrated how sensitive Antarctica is seismic events thousands of miles away.
Sections of Antarctica can see hundreds of micro-earthquakes (dubbed "icequakes") an hour, but in March of2010 the ice sheets vibrated more than usual as a result of an 8.8-magnitude Chilean earthquake, the Georgia Institute of Technology reported. The study was published in the journal Nature Geoscience.
To study the quake's impact on Antarctica the team looked at seismic data from 42 stations in the six hours both before and after the 3:34 a.m event. They found nearly 30 percent of the stations showed evidence of high-frequency seismic signals as the surface-wave hit Antarctica.
"We 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," said Zhigang Peng, an associate professor in the School of Earth and Atmospheric Sciences who led the study. "This 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."
Micro-earthquakes have been found to respond to both shearing and volume deformation from seismic events; these newly-discovered icequakes respond only to volume deformation.
"Such differences may be subtle, but they tell us that the mechanism of these triggered icequakes and small earthquakes are different," Peng said. "One is more like cracking, while the other is like a shear slip event. It's similar to two hands passing each other."
The quakes ranged in duration from one to 10 seconds and varied in in location across the continent. The team found the highest- frequency signals at HOWD near the northwest corner of the Ellsworth Mountains. The triggered ice quakes had similar high waveform patterns. Suggesting the opening of cracks at a single location.
"While 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's frozen ice," Peng said.
