Seismic sensors for the first time attacked the event that developed near an island between Madagascar and Africa. Then alarm bells rang as far as Chile, New Zealand and Canada.
Also Hawaii, almost exactly on the other side of the planet, has picked up the "event".
Nobody knows what it was. 19659002] Meteorite? Submarine volcano nuclear test?
"I do not think I saw anything like that," reports National Geographic, seismologist at Columbia University, Göran Ekström. "That does not mean that the cause for her is ultimately the exotic."
At the center of the mystery is the small island of Mayotte, which lies about halfway between Africa and Madagascar. It has been exposed to an earthquake swarm since May. Most were minor, but the largest ̵
But the earthquake swarm had declined before the mysterious ringing was discovered earlier this month.
Ekström, who specializes in unusual earthquakes, points out that the November 11 event was strange. It was as if the planet were ringing like a bell, sustaining a low-frequency monotone as it spread.
Earthquakes are naturally recorded as short-sharp "cracks".
As tensions in the earth's crust suddenly release, impulses of uniquely identifiable seismic waves emanate from there to the outside where the slip occurs.
The first signal is called the primary wave: high-frequency compression waves that radiate in bundles.
Then comes a secondary wave: these high frequency waves tend to "wobble" more.
Only then come the surface waves: These slow, deep rumble tend to linger and can orbit the earth several times.
The November 11 event is characterized by the absence of a primary wave or secondary waves were detected.
All that was registered was the deep, resonating surface wave. And it did not rumble when the surface wave of an earthquake tends to. Instead, a much cleaner – almost musical – frequency was retained.
National Geographic reports that the French Geological Survey suspects that a new volcano could develop off the coast of Mayotte. While the island was created by volcanic activity, it has been slumbering for more than 4,000 years.
The French believe that the strange ringing was caused by a movement of magma about 30 miles offshore and under deep water. This is supported by GPS sensors, which find that Mayotte has moved two centimeters southeast in less than five months.
However, this is a poorly mapped region. What exactly is under the oceans, one can only guess.
Ekström believes that the unusually pure signal may be due to magma floating around in a chamber or being forced through a gap in the subterranean rocks.
But he is not sure