For decades, Antarctica was thought to be an extremely quiet place in terms of seismic activity. Its eastern region, in specific, stood out for its vast, white stretches of ice, making it appear calmer than the rest of the continent at certain times of the year. However, new research suggests that things might not be as quiet as once thought, as earthquakes do happen in East Antarctica, just like they do in every other part of the world.
As explained by Science Alert, scientists had first detected earthquakes in Antarctica in 1982, and in the two and a half decades or so that followed, only eight more seismic events were detected in the continent. That changed in 2009, when 27 earthquakes were confirmed to have taken place in Antarctica that year, or exactly thrice the number of confirmed events tallied between 1982 and 2008.
Although it might seem like geographical changes in the area were behind the staggering rise in earthquakes in East Antarctica, the study, which was published this week in the journal Nature Geoscience, stresses otherwise. Instead, it was the “lack of instruments close enough to record the [seismic] events” prior to 2009 that explains the sudden increase in earthquakes, according to Drexel University seismologist Amanda Lough, first author on the new paper. Most of the earthquakes observed in 2009 were caused by rifts, or areas in Earth’s crust where rock is pulled apart.
“The rifts provide zones of weakness that enable faulting to occur more easily, and it may be that the situation here is such that activity is occurring preferentially along these areas of pre-existing weakness,” said Lough.
According to Newsweek, the study marked the first time that scientists were able to substantially document earthquake activity in East Antarctica, as Lough and her colleagues used a network of sensors across the region to gather the data back in 2009. This was a significant change from previous attempts to collect data, where researchers had access to a few permanent stations, but none covering the interior part of East Antarctica.
The Newsweek report further explained the researchers’ methodologies, as the team made efforts to eliminate the possibility of false positives, first by burying the sensors in the ice, as that prevented them from detecting earthquakes in the wind, then by calculating each signal’s depth to make absolutely certain that they came from the land below East Antarctica, and not from mere ice sheet movement. Science Alert noted that the sensors were first set up for installation in 2007, in hopes of giving scientists an “unprecedented glimpse” at the seismicity of a continent considered to be the world’s quietest.
Fortunately, the earthquakes detected in East Antarctica in 2009 could be considered mild ones, as none of them exceeded a magnitude of 4 on the Richter scale. But even if the researchers doubt that the tremors were strong enough for the average person to feel, their findings notably countered previous observations that Antarctica is completely calm and uneventful when it comes to seismic activity, as the continent’s heavy ice sheets were thought to be thick enough to suppress earthquakes. Furthermore, the researchers found that minor earthquake activity was similar in both East Antarctica and the Canadian Shield, instead of being less pronounced in the former, based on the team’s calculations.