Co-author of the study Simone Cesca, seismologist at the research center Science German Geology GFZ in Potsdam said: “There have been similar volcanic eruptions elsewhere on Earth, but this is the first we’ve observed in Antarctica.”
The quake struck around the Orca Seamount, a dormant volcano 900 meters above the sea floor in Bransfield Strait, a narrow passage between the South Shetland Islands and the northwestern tip of Antarctica. In this area, the Phoenix tectonic plate is dipping beneath the Antarctic tectonic plate, creating a network of fault zones, stretching some parts of the crust and opening cracks in others.
Scientists at research stations on King George Island, one of the South Shetland Islands, were the first to feel the shock from small earthquakes.
The researchers had to use data from these seismic stations, as well as data from two ground stations of the global navigation satellite system, to measure ground displacement. They also examined data from more distant seismic stations and from orbiting satellites that use radar to measure displacement near the ground.
By compiling this data, the team was able to create a picture of the underlying geology that caused this massive earthquake.
The two largest earthquakes in the series were the 5.9 magnitude earthquake in October 2020 and the 6.0 magnitude earthquake in November. After the November earthquake, seismic activity gradually subsided.
Research shows earthquakes on King George Island appear to have shifted by 11 centimeters. Only 4% of this shift can be directly explained by the earthquake. Scientists suspect that the movement of magma into the crust is largely responsible for the dramatic shifting of the ground.
If there is an underwater eruption, it’s likely that it happened at that time, the researchers added. But so far there is no direct evidence of an outbreak. To confirm that the giant volcano erupted, scientists must send a research team into the strait to measure the depth of the sea floor and compare it to historical maps.