Seismic sensors first took events that came from near the island between Madagascar and Africa. Then, alarm bells began ringing as far as Chile, New Zealand and Canada.
Hawaii, almost exactly on the other side of the planet, also takes on events.
Nobody knows what that is.
Meteorite? Underwater volcano? Nuclear test?
"I don't think I've seen anything like this,"National geography Colombian University seismologist Göran Ekström said. "That doesn't mean that, in the end, the cause is exotic."
At the center of the mystery is the small island of Mayotte, positioned about halfway between Africa and Madigascar. It has experienced a swarm of earthquakes since May. Most are small, but the largest – on May 8 – is the largest in history recorded on the island, surpassing magnitude 5.8.
But the earthquake horde had dropped before the mysterious ring was detected earlier this month.
Ekström, who specializes in unusual earthquakes, shows a lot about the events of November 11 that are strange. As if the planet was ringing like a bell, maintaining a monotonous low frequency when it spread.
Earthquakes, by their nature, are usually listed as & # 39; slits & # 39; short sharp. When tension in the Earth's crust is suddenly released, waves from clearly identifiable seismic waves emit out from the place where slippage occurs.
The first signal is called the main wave: a high frequency compression wave that radiates in a cluster.
Then a secondary wave appears: this high frequency wave tends to & # 39; stretch & # 39; rather more.
Only then does a surface wave emerge: crisp, slow and deep tend to linger, and can circle the Earth several times.
The November 11 incident is famous because no primary or secondary waves were detected.
All listed are deep and resonating surface waves. And that's not rumbling & 39; because earthquake surface waves tend to. Instead, he maintains a cleaner frequency – almost like a musical.
National Geographic reported the French Geological Survey suspects a new volcano might develop off the coast of Mayotte. While the island was made by volcanic activity, it has been active for more than 4000 years.
The French believe that strange ringing may be produced by the movement of magma about 50 km from the coast and under deep water. This is supported by a GPS sensor that detects Mayotte has moved around 5cm to the southeast in less than five months.
But that is a poorly mapped area. Actually what is under the ocean is only predictable.
Ekström believes that unusually pure signals can be caused by magma spilling in a chamber, or being forced to penetrate gaps in subsurface rocks.
But he is not sure.