Icequakes indicate movement of Antarctic glaciers

(ORDO NEWS) — A seismic survey within the Perunik Glacier on Livingston Island in Antarctica has revealed a variable frequency of icequakes, possibly related to ice melting.

For more than 30 years, research on glacial seismicity – the frequency of non-tectonic seismic events in ice – has focused on Greenland, and for good reason. Greenland’s “ice quakes”, as scientists call the tremors in glaciers, are increasingly breaking records, raising concerns about the effects of melting glaciers and climate change.

At the opposite pole of Antarctica, seismicity is also largely due to the movement and breakdown of ice in the thick layer that covers the continent. As a global phenomenon, icequakes indicate a greater correlation between climate change and ice mass, and icequakes can serve as indicators of the general state of glacial ice – more icequakes, more melting. As part of an ongoing project, Gergana Georgieva, a seismologist at the Bulgarian Academy of Sciences and Sofia University, and her colleagues are studying seismic activity in the Antarctic Perunik Glacier, located next to the Bulgarian base of St. Kliment Ohridski on Livingston Island.

Tracking Antarctic Ice Earthquakes

Antarctica is a remarkably seismically active region, and the behavior of glaciers is critical to understanding both basic topography and climatic influences on the region.

There is one Bulgarian seismic station near the Perunik glacier, which has been recording seismic events during the Australian summer since 2015. From January 2020, the station will collect data all year round. Such studies have never been carried out in the area, Georgieva says. By monitoring these icequakes, Georgieva’s team pinpointed the location of more than 16,000 events – a daunting feat with just one station. By pinpointing icequake epicenters – a point on the Earth’s surface just above the seismic event – scientists can better understand the origins of these curious earthquakes, their seasonal variability and changes over time.

Assessment of epicenters and clusters

Georgieva and her team developed a localization code that calculated and mapped the epicenter of events that lasted from one to three seconds. In this code, a sophisticated algorithm determined the direction of the first incoming seismic wave in three dimensions (north / south, east / west, and vertical). Then, by calculating the difference between the first and second incoming seismic waves generated by the event, the code could pinpoint the location of the epicenter. To test this process, Georgieva calculated the epicenter of several earthquakes recorded by both the Bulgarian seismic station and the Spanish research team in the area – the locations coincided.

Through this localization process, the team obtained reliable data from which it was possible to study the frequency and distribution of icequakes. “We traced the events in the glacier and then noticed three clusters of epicenters in different parts of the glacier,” Georgieva says. glacier points in this region.

More time, more events

Seismicity also increased during the study. “We do not yet have enough data to understand how the activity changes over the seasons,” says Georgieva, “so this will be an important next step,” which was made possible by the year-round installation of the station. In addition to tracking changes in seasonal activity, Georgieva and her team will compare seismic data with long-term meteorological information to study the relationship between seismicity and weather, which they hope to ultimately link to climate. 

“Each seismic station and each season of data collection will allow us to better understand the changes in the region,” Georgieva said, “and will give us the opportunity to learn about this glacier and others in the area at different time scales.”

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