Science explains the mysterious tsunami of 2021

In August of last year, a surprise tsunami in the South Atlantic Ocean spread over distances of more than 10,000 kilometers away, crossing the North Atlantic, the Pacific and the Indian Ocean.

It was the first time a tsunami had been recorded. in three different oceans since the 2004 Indian Ocean earthquake, and scientists have just discovered how the waves were triggered, collects ScienceAlert. The epicenter of the August earthquake was measured at 47 kilometers below the ocean floor, which is too deep to initiate a significant tsunami, even one with relatively small waves between 15 and 75 centimeters high.

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However, it turns out that this tsunami was not just the product of a single magnitude 7.5 earthquake. A new look at seismological data suggests that it was actually a series of five sub-earthquakes, and in the middle of them, lurked a much bigger move and shallower than it probably was that triggered the global tsunami.

This third ‘invisible’ earthquake it occurred just 15 kilometers below the Earth’s surface with a magnitude of 8.2. However, in the multitude of earthquakes, our monitoring systems completely missed it. “The third event is special because it was huge and quiet”, explains seismologist Zhe Jia of the California Institute of Technology. “In the data we normally look at for earthquake monitoring, it was almost invisible”He says.

By dividing the seismological data into periods longer than 500 seconds, Jia and his colleagues were able to reveal the presence of an earthquake. slow and shallow never seen before. Among clusters of other regular breakouts, they found a 3-minute move that broke a section of 200 kilometers from the board interface. Together, this single event accounted for more than 70% of the total recorded seismic moment.

“Therefore”conclude the authors of study, “The South Sandwich Island earthquake appears to be a hybrid of deep rupture and slow tsunamigenic slip; this explains the somewhat unusual combination of the relatively great depth and the globally observed tsunami.

New warning systems are urgently needed

The findings suggest that our earthquake and tsunami warning systems must be updated. If we want to warn coastal communities of similar events, then our systems must read between seismological lines to see the largest earthquakes.

Otherwise, the true size of complex earthquakes could continue to go unnoticed. Nowadays, earthquake monitoring systems tend to focus on short and medium periods of seismic waves, but it seems that longer periods also contain important information.

“It is difficult to find the second earthquake because is buried in the first», Jia says. “It’s very rare that complex earthquakes like this are observed… And if we don’t use the right data set, we can’t really see what was hidden inside.”Add.

the geologist Judith Hubbard, who works for the Singapore Earth Observatory and was not involved in the current research, says she is grateful that others are digging into the unexpected tsunami data to better understand where it came from.

“With these complex earthquakes, the earthquake happens and we think, ‘That wasn’t that big, we don’t have to worry.’ And then the tsunami comes and causes a lot of damage, Hubbard says. “This study is a great example of how we can understand how these events work and how we can detect them faster so we can have more warnings in the future», concludes.

Font: 20 minutes

Reference article: https://www.20minutos.es/noticia/4955764/0/mysterious-tsunami-extended-all-world-explained-science/?autoref=true