Seismic sensors are fine-tuned to pick up vibrations in the earth. They’re a useful tool for understanding the patterns of plate movement and seismic activity. Yet a new event has even the most seasoned seismologists befuddled. The planet, they say, just rang like a bell. What this means is a mystery.
The day Earth rang like a bell. Strange seismic waves were picked up circling the globe on November 11, 2018. Instruments picked up the seismic waves more than 16,000 km away—but bizarrely, nobody felt them. Now seismologists are trying to figure out why https://t.co/y7gf9R5vwg pic.twitter.com/X8iscnPppa
— Massimo (@Rainmaker1973) November 29, 2018
“Seismic sensors first picked up the event originating near an island between Madagascar and Africa. Then, alarm bells started ringing as far away as Chile, New Zealand and Canada,” the NY Post writes.
Unlike the average earthquake, this event was picked up across the planet. What started near Madagascar was also picked up in Hawaii.
And the event isn’t registering like an earthquake.
“I don’t think I’ve seen anything like it,” Columbia University seismologist Göran Ekström says. “It doesn’t mean that, in the end, the cause of them is that exotic.”
The cause is the deep mystery. Underwater volcanoes can trigger similar readings, though not at these distances. Nuclear tests register, but not at this scale. A meteorite could do it, though none were reported.
“At the center of the mystery is the tiny island of Mayotte,” NY Post adds, “positioned about halfway between Africa and Madagascar. It’s been subjected to a swarm of earthquakes since May. Most have been minor, but the biggest — on May 8 — was the largest in the island’s recorded history, topping at a magnitude of 5.8.”
The event in question happened on November 11, and Ekström has noted that the readings from it were most atypical. Unlike the short and violent hit seen from an earthquake, this one provide a long monotone reading.
“The first signal [of an earthquake] is called a primary wave: high-frequency compression waves that radiate in bunches,” The Post writes.
“Then comes a Secondary wave: These high-frequency waves tend to ‘wiggle’ more.”
Earthquake behavior is predictable, and even has allowed for tsunami early-warning systems to be installed in danger prone areas.
Ekström notes that this event didn’t have the first parts of the earthquake waves. There was no sharp start. Instead, the tone was more sustained and clear.
The best guess at this point seems to point to the volcanic activity deep below Mayotte. A hypothesis is building that suggests magma in a deep chamber may be sloshing about and causing the bell-like tone.
What that means, though, is still uncertain. Could this tone indicate a big earthquake is on the way? Or does this mean a massive underwater volcano is about to erupt? For now, even the experts don’t know.