The waves emanated off the shores of Mayotte island and set off geological sensors across the world.
A series of unusual, almost undetected earthquake-like seismic waves that generated in the Indian Ocean and lasted for 20 minutes on November 11 has left scientists puzzled. The ripples, which were originated 15 miles off the shores of a tiny island Mayotte in the Indian Ocean around 9:30 am UT were not felt or noticed by any human.
But machines detected them.
According to a National Geographic report, the waves emanated off the shores of Mayotte island and reverberated across Africa, setting off geological sensors in Zambia, Kenya, and Ethiopia. Crossing the Atlantic, they were also picked up by sensors in Chile, New Zealand, Canada, and even Hawaii.
As no humans felt, they went undetected at the time. However, a person monitoring the US Geological Survey’s live stream of seismogram noticed the waveform.
A Twitter user posted the waveforms, Sparking the interest of other geologists and earthquake enthusiasts. Posting the unusual waveforms, Twitter user @matarikipax described them as “a most odd and unusual seismic signal”.
The waveform that he posted were recorded at Kilima Mbogo, Kenya.
According to a report in the Independent, the power of the seismic waves, as well as the curiously regular shape of the waveform, puzzled scientists when they started to examine the readings.
How are they different from regular earthquake waveform?
In case of a typical earthquake, the rapid crash of a tectonic plate movement sends out what is known as a “wave train” which is composed of several types of waves moving at different speeds from the epicentre of the quake.
Seismographs measure the fastest waves first - the primary or P waves - which arrive in an abrupt cluster. After P waves come the secondary waves or S waves and finally slower low-frequency surface waves. These three types of waves move across the surface of the planet several times when an earthquake takes place.
The machine readings on November 11 showed slow-moving waveforms, usually seen following large earthquakes. But interestingly there had been no perceptible earthquake in Mayote. The “monochromatic” waveform has left scientists puzzled.
While earthquakes normally produce waves of so many different frequencies, these readings appear more jumbled. The waveform was a crisp zigzag, which repeated after steady 17-second intervals.
What do the scientists say?
Speaking to the National Geographic, Helen Robinson, a PhD candidate in applied volcanology at the University of Glasgow, said, "They're too nice. They're too perfect to be nature."
She added that the location of the island means industrial sources for the unusual wave - such as oil drilling or from wind farms - could be ruled out.
Jamie Gurney, the founder of UK Earthquake Bulletin (UKEQ) who was among those who began looking at the waveform, said on Twitter that he had “no idea if a similar global signal of this nature has ever been observed”.
"I don't think I've seen anything like it," Colombia University seismologist Göran Ekström told National Geographic. "It doesn't mean that, in the end, the cause of them is that exotic."
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 "Waveform recorded at Kilima Mbogo, Kenya on Nov 11 (Source: USGS)")
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