It isn't exactly earth-shaking news for tectonic plates to shift in the Antarctic: hundreds of these events, known by some as "icequakes," can occur every hour. However, a new research study done at the Georgia Institute of Technology shows that in 2010, an earthquake as far away as Chile caused the earth to shake harder than it normally would in the Antarctic.
Chile is over 3,000 miles from Antarctica, so this may seem strange. The research study, led by Zhigang Peng, is the first to suggest that the earth in Antarctica can be affected by seismic events from far-off countries. The study was published on August 11 in Nature Geoscience.
The researchers analyzed seismic waves from 42 different locations in Antarctica. They looked at waves from six hours before the 8.8-magnitude earthquake struck Chile at 3:34 a.m., and six hours after the quake.
To study the quake's impact on Antarctica, the research team looked at seismic data from 42 stations in the six hours before and after the 3:34 a.m. event. They used technology to translate the seismic waves into sound, listening for high-frequency seismic waves in Antarctica. The team found that almost 30 percent of the 42 locations where seismic waves were captured showed clear signs that the Chilean earthquake caused high-frequency seismic waves when it reached 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, the lead researcher on the study. Peng teaches at the Georgia Institute of Technology, School of Earth and Atmospheric Sciences. "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."
According to Peng, there is a subtle difference between micro-earthquakes and the "icequakes" that his team discovered. Micro-earthquakes react to both shearing and volumetric deformation from far-away stressors, while icequakes only react to volumetric 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 duration of the icequakes ranged from 1 to 10 seconds and spanned the continent all the way to the South Pole. It is difficult to place the source locations of the icequakes because there is not enough seismic coverage of Antarctica; however, the group was able to determine that at least some of the waves originated near the surface, because they generated surface waves.