From: Carolyn Gramling, Science
Published August 11, 2014 07:34 AM

Icequakes triggered by earthquakes

In 2010, a powerful magnitude-8.8 earthquake struck off the coast of central Chile, rocking much of the country and producing tremor as far away as Argentina and Peru. But a new study suggests its effects were felt even farther away - in Antarctica. In the wake of the Maule temblor, the scientists found, several seismic stations on the frozen continent registered "ice quakes," probably due to fracturing of the ice as the planet's crust shook.

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Earthquakes are already known to affect Antarctica's ice shelves, thanks to the tsunamis they can spawn. Tsunami waves can propagate for great distances across the ocean; if the waves reach Antarctica's ice shelves - the floating platforms of ice surrounding the continent - they can push and pull on the ice, promoting fractures and ultimately helping large chunks of ice break off, or calve.

But whether earthquake seismic waves, traveling through the ground, can chip away at Antarctica’s ice sheet - the ice piled on top of the continent - remained an unanswered question. Zhigang Peng, a geophysicist at the Georgia Institute of Technology in Atlanta, found the answer by accident while studying effects of the Chile quake in South America. His team was looking for surface waves - shallow seismic waves that travel along the planet’s crust rather than going deeper into the mantle. Surface waves come in two basic types: Love waves, which shake the ground from side to side; and Rayleigh waves, which move in a rolling motion, compressing and expanding the ground as they travel. Both types of surface waves can in turn trigger numerous microearthquakes, called tremor.

Peng didn't initially intend to look at signals from Antarctic seismic stations, but data from a few somehow sneaked onto their research list. And when his team looked for the surface wave signals at those stations, "we found something very interesting," Peng says. "We started to find tiny seismic signals that we believe are associated with ice cracking."

Antarctica landscape image via Shutterstock.

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