A Mystery Seismic Wave Just Swept Earth—But Scientists Can't Work out Why

Scientists are baffled by a strange seismic ripple that traveled around the globe the morning of November 11.

Seismic waves buzzed sensors from Africa to New Zealand and Hawaii for about 20 minutes, but it seems no humans felt the bizarre ripple, National Geographic reported.

Twitter user matarikipax spotted the strange motion on U.S. Geological Survey graphs. He noticed a "most odd and unusual seismic signal" on data from Kilimambogo, Kenya; Lusaka, Zambia, Mount Furi, Ethiopia; San Pablo, Spain; and Wellington, New Zealand.

This is a most odd and unusual seismic signal.
Recorded at Kilima Mbogo, Kenya ...#earthquakehttps://t.co/GIHQWSXShd pic.twitter.com/FTSpNVTJ9B

— ******* Pax (@matarikipax) November 11, 2018

The signals, National Geographic reported, resembled the long-period surface waves that rumble out from earthquakes alongside other higher-frequency waves. But there was no major earthquake that morning to set off the ripple.

Stranger still, the waves were monochromatic, stripped of the fuzzy noise that multiple different frequencies create.

"I don't think I've seen anything like it," Göran Ekström, a seismologist at Columbia University, told National Geographic.

"It's like you have colored glasses and [are] just seeing red or something," added Anthony Lomax, an independent seismology consultant.

Some scientists think the weird ripple might be something to do with a seismic storm lashing Mayotte, an archipelago in Africa near where the signal began. But that storm has declined in ferocity since a magnitude 5.8 tremor struck in May.

The French Geological Survey (BRGM), National Geographic stated, suspects a new center of volcanic activity could be emerging near the island. Magma might be on the move deep below the ocean some miles from the shores.

An incredibly slow earthquake, which released stress over a long period of time, could also have caused the strange ripple, Ekström told the publication. Such events, often linked to volcanic activity, can last from minutes to days. "The same deformation [as a regular earthquake] happens, but it doesn't happen as a jolt," Ekström said.

But scientists are still far from certain. "It is very difficult, really, to say what the cause is and whether anyone's theories are correct," Helen Robinson, a doctoral candidate in applied volcanology at the University of Glasgow, told National Geographic.

Explanations as fanciful as a sea monster, a weapons test or an alien attack have all been shared online. BGRM plans on probing the bottom of the ocean near Mayotte to see if a submarine eruption occurred. But for now, at least, the enormous planet-sweeping ripple of November 11 remains a mystery.