Polar ice river emits seismic signals

ST. LOUIS, June 10 (UPI) -- A U.S.-led team of seismologists has discovered seismic signals from an Antarctic ice river that they say make California earthquakes sound trivial.

Professor Douglas Wiens of Washington University in St. Louis and colleagues at Pennsylvania State University and Britain's Newcastle University say two seismic wave bursts come from the ice stream every day, each one equivalent to a magnitude 7 earthquake.

The ice stream is essentially a giant glacier 60 miles wide and one-half mile thick that moves about 18 inches in 10 minutes, remains still for 12 hours, then moves another 18 inches, the researchers said.

"By some measures, the seismic impact is equivalent to a very large earthquake but it doesn't feel like it because the movement is much slower than a real earthquake," Wiens said. "I guess you could call it an earthquake at glacial speed.

"This is very strange behavior and we need to understand what controls the speed of the ice streams, because that will affect how fast the ice in Antarctica will go away and sea level will rise as global warming melts the West Antarctic Ice Sheet."

The study appeared in the June 5 online issue of the journal Nature.