Scientists say that Antarctica is Shaking due to ‘Earthquakes’

Scientists say that Antarctica is Shaking due to ‘Earthquakes’

Slow yet vigorous interior massive tremors known as ‘Ice Quakes’, caused by the sudden movement of ice over rough patches of rock within glacier or by fracturing crevasses (which according to some measurements are the equivalent of magnitude-7 earthquakes), are making Antarctica tremor.

Ice Quakes differentiate, however, from the conventional micro-quakes and tremors triggered by both Love and Rayleigh surface waves. Surface waves come in two basic types. Love waves, which shake the ground from side to side while Rayleigh waves, which move in a rolling motion, compress and expand the ground as they travel. Both types of surface waves can in turn trigger numerous microearthquakes, called tremor. Although micro-quakes can be triggered by both shearing and volumetric deformation from distant events, icequakes only occur in response to volumetric deformation. Ziagang Peng, a Seismologist at the Georgia Institute of Technology in Atlanta who is the Lead Author of the study, explained that by saying,

“Such differences may be subtle, but they tell us that the mechanisms of these triggered icequakes and small earthquakes are different.”

He was studying and analyzing the effects of the Chile quake in South America when out of the blue moon, he found the answer to a long-lasting query. Whether Earthquake seismic waves, traveling through the ground, chip away at Antarctica’s ice sheet (the ice piled on top of the continent) or not? He and his team were originally looking for surface waves, the shallow seismic waves that travel along the planet’s crust rather than going deeper into the mantle, but they got a lot more than that as he himself acknowledged in the following words:

“Regular Ice Quakes probably occur all the time in Antarctica and other polar regions. What we found is that they occurred more during the seismic waves of the Maule event.”

Antarctica’s trembling became substantial when ice snapped and popped because of a major earthquake in Maule, Chile. Antarctica has faced massive earthquakes in the past like the one in March 2011 when Japan’s Tohoku tsunami tore off two Manhattan-size icebergs from the Sulzberger Ice Shelf. Having said that, this is the first occasion when a distant earthquake prompted Ice Quakes in this icy continent. On February 27, 2010, an earthquake having a magnitude of 8.8 struck the subduction zone off the coast of Chile. This disastrous and horrific earthquake resulted due to Rayleigh surface waves which are strong seismic waves that ripple around the Earth racing as fast as the speed of sound before tapering off and rolling along like a wave in a lake or the ocean.

Expedition in Antarctica

These powerful seismic waves initiated small earthquakes in many different tectonic settings, including Antarctica. As the surface waves moved across the white continent, one-third of Antarctic seismic stations reported shaking coming from so-called Ice Quakes. According to the reports of the study, the Ice Quake shaking at different stations occurred as the Rayleigh waves traveled across rock beds under the glaciers in Antarctica. At some stations, a short Ice Quake burst was also observed from a seismic ‘P wave’ which travels through the Earth’s interior.

According to Peng, most of the small icequakes were triggered during or immediately after the passing of long-period Rayleigh waves generated from the Chilean mainshock. He mentioned this in one of his studies that were published in August 2014. Some were quick bursts, ending in less than a second, whereas others resembled tremor-like signals up to 10 seconds long. He said,

“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 ice. Such ice quakes are improbable to present a significant hazard but the new finding adds another type of seismic phenomenon to the literature that can be triggered by large distant events.”

Peng and his colleagues are ready to appraise the data from older great earthquakes to see if they also brought forth Ice Quakes. Walter is also testing whether distant earthquakes may momentarily change the speed of glaciers, by causing them to suddenly unstick and slide. Walter concluded it by saying,

 “It’s an interesting result. A big earthquake on the other side of the world can shift things in the Earth and make it crack.”

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