A hidden earthquake triggered a global tsunami and caught experts by surprise

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Satellite image of the August 2021 tsunami (credit: NOAA Center for Tsunami Research)

A surprise tsunami in the South Atlantic Ocean spread more than 10,000 kilometers across the North Atlantic, Pacific and Indian Oceans in August last year. It was the first time a tsunami had been recorded in three different oceans since the tragic ocean earthquake Indian from 2004.

Fortunately, there were not thousands of fatalities, as in 2004, but something went wrong with the warning systemsand now scientists have just discovered how the events were triggered.

“In about 20 or 25 minutes we realized that something strange was happening” with those words, Stuart Weinstein, deputy director of the Pacific Tsunami Warning Center, described what he saw in his control systems: the algorithms that characterize earthquakes were failing, and a a few minutes later a tsunami was triggered that would send waves that would travel around the world, in August 2020.

Now, new research suggests that a hidden earthquake near the South Sandwich Islands in the South Atlantic, larger than initial estimates that tsunami from the islands east of the southern tip of South America to Alaska.

The hidden quake, which rumbled beneath remote ice-covered islands, initially went unnoticed because it was part of a complex series of tremorsaccording to a study published Tuesday in the journal Geophysical Research Letters.

The new investigation determined that what actually occurred were five earthquakes over several minutes, including a much shallower magnitude 8.2 quake that early reports failed to identify (Getty).

The researchers described that the August 2021 earthquake on the South Sandwich Island of magnitude 8.2 on the Richter scale This was a surprise, because it was initially reported as a magnitude 7.5 event at a depth of 47 km, but generated a globally spreading tsunami that would only be expected for a larger, shallower event.

“We noticed the tsunami right away”, He said Summer Ohlendorfscientific officer of the United States National Tsunami Warning Center, which was not part of the new research. “It was a little bit larger than expected based on the parameters of the earthquake.”

The new investigation determined that what actually happened was five earthquakes over several minutes, including a much shallower magnitude 8.2 quake that early reports failed to identify and likely caused the tsunami, this was the hidden quake missed by scientists. Findings from this study could help improve earthquake warning systems to better respond to unusual and complex events.

Why couldn’t scientists anticipate the tsunami? “The seismic signals from all these events interfered with each other because they occurred in close succession” explained Zhe Jia, a seismologist at the California Institute of Technology and lead author of the study.

The initial earthquake masked the more powerful and slower earthquake, which was the third in the series.

A surprise tsunami in the South Atlantic Ocean spread more than 10,000 kilometers across the North Atlantic, Pacific and Indian Oceans in August last year (Getty)

“The third was very special and quiet,” said the seismologist. “A huge, hidden, slow event like the third sub-event could lead to a significant underestimation of tsunamis.”

“It was powerful enough to spread throughout the Southern Ocean and throughout all the major ocean basins. It was recorded by sea level stations around the world,” Weinstein said, adding that “There are no hard and fast rules about when a tsunami can cause a flood because it very much depends on the nature of the affected coastline. But when the waves exceed one meter (three feet in altitude) is when “you have to worry about the threat of flooding”.

The South Sandwich Islands are a series of small volcanic landmasses that lie more than 1,000 miles from the southern tip of South America. About half of the islands’ landscape is permanently covered in ice.

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