June 16, 2026 [ report
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Krystal Kasal
Author
Gaby Clark
Scientific Editor
Robert Egan
Associate Editor
Most of the earthquakes we hear about are due to tectonic plates colliding or sliding past each other near plate boundaries. Yet researchers have detected some enigmatic earthquakes happening inside the more stable interiors of plates. Intermediate-depth earthquakes (IDEs), which occur around 70–300 kilometers (43–186 miles) below the surface, are especially puzzling because rocks at those depths are hot enough to flow more fluidly.
A group of scientists recently found a way to take a deeper look into this phenomenon. Using new machine-learning tools, the group re-examined old seismic data from Antarctica. Their results, published in Science, revealed hundreds of previously undiscovered IDEs far from plate boundaries.
The mystery of deep interior earthquakes #
Intraplate earthquakes have been identified in a few areas, like the Hindu Kush in Afghanistan and the Atlas Mountains in Morocco, but their causes have been debated. Some researchers attribute them to paleosubduction, where old oceanic lithosphere was thrust deep into the Earth's mantle, leaving behind detached slab remnants; continental lithospheric delamination, where the dense lower portion of a tectonic plate's mantle detaches and sinks into the hotter, more fluid asthenosphere below; or "drip tectonics," where thick mantle lithosphere stretches and sinks into the asthenosphere. But the authors of the new study say that the evidence is unclear for any of these possible causes.
"Our understanding of intraplate IDEs has been hindered by a lack of both reliable event identification and accurate earthquake locations. Although some large-magnitude intraplate IDEs have been documented, most have moment magnitudes <5, and such earthquakes may have weak or emergent P-wave or S-wave arrivals that can easily be misidentified. When combined with sparse seismic station coverage, it can be difficult to robustly identify, locate, and determine source mechanisms for these events," the team writes.
Deep-learning unveils Antarctica's hidden earthquakes #
The researchers decided to look at recent advances in machine learning-based seismic event detection. Similar automated detection techniques have found previously unrecognized seismic activity in East Antarctica, which was thought to be a seismically inactive area. So the team applied a deep-learning earthquake detection system to seismic data from 49 different stations in northern Victoria Land, spanning multiple deployments between 2001 and 2015. The algorithm automatically picked P- and S-wave arrivals and generated a catalog of 1,068 events beneath David Glacier in East Antarctica.
Of the events detected, 510 were IDEs (more than 70 km deep) with magnitudes ranging from 1.6 to 3.5. They found that the events occurred in the upper mantle, near the boundary between the thick, cold East Antarctic lithosphere and the thinner, warmer West Antarctic lithosphere. Another shallower group of events occurred at depths of 0 to 40 km. The team notes that it evaluated the accuracy and robustness of event detections and relocations with a series of assessments, although the depth and location uncertainties are still on the order of tens of kilometers.
"Events within the crust (~3 to 40 km depth) could be induced by stress changes resulting from ice movement and mass redistribution, a mechanism that has been suggested as the source of seismicity beneath Thwaites Glacier in West Antarctica and beneath the Greenland Ice Sheet. However, the deeper, upper-mantle events that form the focus of our study challenge most prior IDE mechanism suggestions," the study authors write.
An interplay between lithospheric bending and heavy ice #
The team says that the studied region was not associated with active subduction, meaning dehydration embrittlement leading to brittle failure was unlikely. The researchers also say that tomographic images of the seismic velocity structure beneath northern Victoria Land showed no remnant slabs, lithospheric delamination or drip tectonics, which were suggested as the cause of intraplate IDEs in other locations.
Instead, the team says the pattern and mechanisms of these events match predictions from geodynamic models that indicate stresses concentrate where mantle flow meets sharp changes in plate thickness and strength. This causes a flexural "bending" of the East Antarctic lithosphere (the rigid, brittle layer comprising the crust and the top portion of the upper mantle). This bending occurs when the cold, rigid crust and upper mantle interact with warmer, softer rock, and the difference leads to variation in tectonic strength. The team also says the load of the ice sheet above adds additional stress, helping to trigger these quakes.
"Understanding the isostatic response to changes in the Antarctic ice sheet and its impact on lithospheric deformation is an ongoing area of research, but these processes can contribute to the stress conditions near David Glacier, and this complex interaction between the cryosphere, lithosphere, and asthenosphere could further promote the identified IDEs," the study authors write.
The team also says that the results imply that similar intraplate IDEs may be common worldwide but have gone undetected because of limited seismic coverage and older analysis methods. However, the deep-learning detection methods used in this study may be useful in future intraplate IDE detections.
Written for you by our author Krystal Kasal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.
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Publication details
Long M. Ho et al, Upper-mantle earthquakes beneath East Antarctica, Science (2026). DOI: 10.1126/science.aea9895 Journal information:
[Science](https://phys.org/journals/science/)
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](http://www.sciencemag.org/)
Key concepts
oceanic lithosphere© 2026 Science X Network
Citation: Deep learning helps discover hundreds of Antarctic earthquakes coming from an unlikely location (2026, June 16) retrieved 17 June 2026 from https://phys.org/news/2026-06-deep-hundreds-antarctic-earthquakes.html