Scientists have access to precise, long-term data on polar tremors

Aug 24, 2012 09:38 GMT  ·  By
This chart shows temperature anomalies caused by global warming in Antarctica, between 1957 and 2006
   This chart shows temperature anomalies caused by global warming in Antarctica, between 1957 and 2006

Between 2002 and 2003, the Transantarctic Mountains Seismic Experiment gathered earthquake data from the David Glacier in Antarctica. These datasets may now help geologists learn more about how stick slip fault lines work.

The work also contributes significantly to understanding how glaciers move across the surface of the Southern Continent. This is very important for models that try to predict how global warming will influence the amount of ice Antarctica puts in the Southern Ocean annually.

Geoscientists at the Pennsylvania State University (Penn State) say that TMSE data were recently coupled with information provided by the Global Seismic Network (GSM) station Vanda.

Over the course of a single year, the two datasets revealed 20,000 earthquakes at David Glacier, occurring at very regular intervals, of just 25 minutes (give or take 5 minutes). The tremors are most likely produced by ice flowing above a buried hill.

“Our leading idea is that part of the bedrock is poking through the ductile till layer beneath the glacier,” explains Penn State expert Lucas K. Zoet. PhD. The underground structure is believed to be around half a mile (~800 meters) in diameter.

“No one has ever seen anything with such regularity. An earthquake every 25 minutes for a year,” the expert adds. Details of the new study were published in the latest issue of the top journal Nature Geoscience.

As the ice flows over the hill, the movements create a stick slip situation that is very similar to how the San Andreas fault line works, on the US West Coast. What is interesting to note here is that the ice masses do not move smoothly, but rather in a jerky, step-by-step manner that produces tremors.

The seismic instruments that worked with Vanda on the study were since removed from David Glacier and transferred elsewhere. At this point, only the GSM station is providing data on what's going on at this location, and researchers are saying that the lack of additional data is frustrating.

The study was sponsored by grant money from the US National Science Foundation (NSF).