Hidden magnitude-8.2 earthquake source of mysterious 2021 global tsunami

Scientists have uncovered the source of a mysterious 2021 tsunami that sent waves around the globe.

In August 2021, a magnitude 7.5 earthquake hit near the South Sandwich Islands, creating a tsunami that rippled around the globe. The epicenter was 47 kilometers below the Earth's surface — too deep to initiate a tsunami — and the rupture was nearly 400 kilometers long, which should have generated a much larger earthquake.

A new study revealed the quake wasn't a single event, but five, a series of sub-quakes spread out over several minutes. The third sub-quake was a shallower, slower magnitude 8.2 quake that hit just 15 kilometers below the surface. That unusual, "hidden" earthquake was likely the trigger of the worldwide tsunami.

The study was published in the AGU journal Geophysical Research Letters, which publishes short-format, high-impact papers with implications that span the Earth and space sciences.

"I think a lot of people are daunted by trying to work on events like this," said Hubbard. "That somebody was willing to really dig into the data to figure it out is really useful."

Both Jia and Hubbard noted a long-term goal is to automate the detection of such complex earthquakes, as we can for simple earthquakes.

To read the full AGU press release click here.