A single volcano has produced the largest recorded seismic activity in this region. The culprit is the Orca seamount in Antarctica, according to an international team of scientists in a recent study published in the journal Communications Earth and Environment.
The research shows that such events can be studied and described in great detail even in areas as remote as Antarctica.
Led by Simone Cesca of the German Research Center for Geosciences (GFZ) in Potsdam, researchers from Germany, Italy, Poland and the United States participated. With the combined application of seismological, geodetic and remote sensing techniques, experts were able to determine how the rapid transfer of magma from the Earth’s mantle near the crust-mantle boundary to near the surface led to the 85,000 swarm earthquake. earthquakes in just three months.
record sequence
The swarm, which began in August 2020 and subsided in November of that year, and the earthquakes were likely caused by a “finger” of hot magma penetrating the crust, according to this research.
The swarm occurred around the Orca Seamount, a dormant volcano that rises 900 meters – and a base diameter of about 11 kilometers – from the seafloor in Bransfield Strait, a narrow passage between the South Shetland Islands and the tip northwestern Antarctica. In this region, the Phoenix tectonic plate plunges under the continental Antarctic plate, creating a network of fault zones, stretching some portions of the crust and opening cracks elsewhere.
Swarm earthquakes occur mainly in volcanically active regions, hence the movement of fluids in the Earth’s crust is suspected to be the cause.
“In the past, the seismicity in this region was moderate. However, in August 2020 an intense seismic swarm began there, with more than 85,000 earthquakes in half a year. It represents the largest seismic upheaval ever recorded there ”, reports Simone Cesca, co-author of the work.
At the same time as the swarm, a lateral ground shift of more than four inches and a small uplift of about a centimeter was recorded on neighboring King George Island.
Challenges in a remote area
To reconstruct the chronology and development of the disturbances and determine their cause, the team also analyzed data from more distant seismic stations and data from InSAR satellites, which use radar interferometry to measure ground displacements. The presence of a volumetric magma intrusion can be confirmed independently on the basis of geodetic data.
The two largest earthquakes in the series were a magnitude 5.9 earthquake in October 2020 and a magnitude 6.0 earthquake in November. If there was an underwater eruption at the seamount, it probably happened at that time, experts add. But, at the moment, there is no direct evidence of an eruption at this seamount.
“Our study represents a successful new investigation of a seismic-volcanic disturbance in a remote location on Earth, where the combined application of seismology, geodesy and remote sensing techniques are used to understand seismic processes and magma transport in poorly instrumented areas. . This is one of the few cases where we can use geophysical tools to look at magma intrusion from the upper mantle or the crust-mantle boundary into the shallow crust: a rapid transfer of magma from the mantle to near the surface. that takes only a few days”, concludes Cesca.
Referencia: Simone Cesca, Monica Sugan, Łukasz Rudzinski, Sanaz Vajedian, Peter Niemz, Simon Plank, Gesa Petersen, Zhiguo Deng, Eleonora Rivalta, Alessandro Vuan, Milton Percy Plasencia Linares, Sebastian Heimann, Torsten Dahm. Massive earthquake swarm driven by magmatic intrusion at the Bransfield Strait, Antarctica. Communications Earth & Environment, 2022; 3 (1) DOI: 10.1038/s43247-022-00418-5
