Mysterious seismic waves in the Indian Ocean that were picked up by monitoring stations from Madagascar to Canada three weeks ago have baffled scientists.
Researchers and earthquake enthusiasts who spotted the signals have narrowed down the origin to a region just off the coast of the island Mayotte.
The slow waves detected on November 11 rumbled for more than 20 minutes, unbeknownst to most people.
They are similar to those typically seen after large earthquakes, which are known to travel great distances – but, no such earthquake took place.
Theories as to what caused the cryptic rumble include an undetected meteor strike or underwater volcanic eruption.
Researchers and earthquake enthusiasts who spotted the signals have narrowed down the origin to a region just off the coast of the island Mayotte (shown), in the Indian Ocean. But, no one’s quite sure what caused the strange event
‘I don’t think I’ve seen anything like it,’ Göran Ekström, a seismologist at Columbia University who specializes in unusual earthquakes, told National Geographic.
But, he adds, ‘It doesn’t mean that, in the end, the cause of them is that exotic.’
A Twitter thread that garnered attention from the seismology community first revealed the strange phenomenon on the morning of November 11.
‘Confirmation of location places it near the Comoros’, the researchers who made the find says.
‘This is a most odd and unusual seismic signal,’ Twitter user @matarikipax wrote alongside a seismograph reading from Kilima Mbogo, Kenya.
Over the course of that day, many others chimed in to the conversation to point out where else the low-frequency waves were detected: Chile, New Zealand, Canada, and Hawaii.
The signals created by the waves from Mayotte came up clean, with a zigzagging pattern primarily of one type of wave, which took 17 seconds to repeat, according to National Geographic.
Waves like this are known as monochromatic.
The strange waves were traced to an origin roughly 15 miles off of the French island, Mayotte
A Twitter thread that garnered attention from the seismology community first revealed the strange phenomenon on the morning of Nov 11. Scientists and earthquake enthusiasts alike worked to narrow it down
Scientists are working to understand what spurred the mysterious waves on that day.
So far, many suspect they’re related to an ongoing seismic swarm in the region that began last May.
But even then, there was no corresponding earthquake on November 11.
Researchers with the French Geological Survey (BRGM) say it could be a signal that magma beneath the volcanic island is shifting offshore.
Others say there may have been a ‘slow’ earthquake that simply went by unnoticed, or an underwater eruption.
The experts say the complex geology of the region further compounds the issue, potentially filtering some of the waves to make the clean signal, NatGeo reports.
Scientists plan to survey the ocean to find out any additional information that could help to explain the mysterious phenomenon.
But at this stage, the experts agree there’s just too much we don’t know to say what was really to blame.
HOW ARE EARTHQUAKES MEASURED?
Earthquakes are detected by detecting the size, or magnitude, and intensity of the shock waves they produce, known as seismic waves.
The magnitude of an earthquake differs from its intensity.
The magnitude of an earthquake refers to the measurement of energy released where the earthquake originated.
Magnitude is calculated based on measurements on seismographs.
The intensity of an earthquake refers to how strong the shaking that is produced by the sensation is.
A 5.3 magnitude earthquake hit the Channel Islands off the coast of southern California on Thursday at 10.30am
According to the United States Geological Survey, ‘intensity is determined from the effects on people, human structures and the natural environment’.
Earthquakes originate below the surface of the earth in a region called the hypocenter.
During an earthquake, one part of a seismograph remains stationary and one part moves with the earth’s surface.
The earthquake is then measured by the difference in the positions of the still and moving parts of the seismograph.