On the August day that an earthquake hit near the South Sandwich Islands in the South Atlantic last year, scientists knew something strange was happening.
Algorithms that characterize earthquakes were failing, said Stuart Weinstein, deputy director of the Pacific Tsunami Warning Center, which is run by the National Oceanic and Atmospheric Administration. A tsunami was triggered that would send waves traveling around the world.
Now, new research suggests a hidden earthquake — larger than initial estimates — sent that tsunami from the islands just east of South America’s southern tip all the way to Alaska.
The hidden earthquake, which rumbled beneath the remote ice-covered islands, initially went unnoticed because it was part of a complex series of temblors, according to a study published Tuesday in the journal Geophysical Research Letters.
Get a weekly recap of the latest San Francisco Bay Area housing news. Sign up for NBC Bay Area’s Housing Deconstructed newsletter.
The new study says that there were actually five earthquakes over several minutes, including a much shallower 8.2-magnitude earthquake that early reports did not identify and that likely caused the tsunami. The analysis could help spur improvements to earthquake warning systems so they better account for unusual and complex events.