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Just before 9.30am on Sunday 11 November, a series of unusual seismic pulses rippled around the world almost undetected.
The waves rang for over 20 minutes, emanating about 15 miles off the shores of Mayotte - a tiny island in the Indian Ocean between Madagascar and Africa.
From here, they reverberated across Africa, setting off geological sensors in Zambia, Kenya, and Ethiopia.
They crossed the Atlantic, and were picked up in Chile, New Zealand, Canada, and even Hawaii nearly 11,000 miles away, the National Geographic reports.
Despite their huge range, the waves were apparently not felt by anybody. However, one person monitoring the US Geological Survey's live stream of seismogram displays did notice the unusual waveform and posted it to Twitter, sparking the interest of other geologists and earthquake enthusiasts.
[...] The bizarre waveform is what scientists call "monochromatic". Earthquakes normally produce waves of so many different frequencies, the wave readings appear more jumbled.
But the mystery waveform from Mayotte was a crisp zigzag, which repeated after steady 17-second intervals.
"They're too nice. They're too perfect to be nature," joked the University of Glasgow's Helen Robinson, who is study[ing] for a PhD in applied volcanology.
(Score: 2) by c0lo on Thursday December 06 2018, @01:44AM (5 children)
Deep focus Earthquakes [wikipedia.org] - characterized by almost no surface waves at all and little reverberations - thus the waves travel long distances. They are usually less destructive due to the absence of surface waves, but can be still in "the big ones" category by the amount of energy released.
By themselves, they can occur with no tectonic fault displacement (but are usually the cause of subsequent shear-stress shallow focus quakes by the extra strain they cause in nearby faults).
They are mainly caused by chemical (lost of crystallographic water or thermal runaway) and/or phase (under pressure, the material transit into a more denser crystallographic form) transformations.
(a deep-focus quake can be another possible explanation for the one that's the TFA subject. Still, the almost monochrome frequency is weird).
Given the range of temperatures between the upper and lower layer of the crust, definitely there'll be order of magnitude differences.
The deep focus quakes will involve rocks in almost their plastic phase (fracturing rock aren't the cause), the shallow quakes will involve hard rocks.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1) by khallow on Thursday December 06 2018, @03:21AM (4 children)
Surface waves are indicative of near surface earthquakes.
(Score: 2) by c0lo on Thursday December 06 2018, @03:41AM (3 children)
vs my:
You know? Like a PET bottle one has stepped on and which slowly gets to a configuration closer to the non-deformed shape, occasionally popping when a crease gets smoother.
Still a hypothesis (which I don't have time or resources to investigate).
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1) by khallow on Thursday December 06 2018, @07:34PM (2 children)
(Score: 2) by c0lo on Friday December 07 2018, @01:45AM (1 child)
Let us note that those distortions are present with or without post glacial rebound.
Expecting the rebound to have no detectable effect on global scale is unreasonable.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1) by khallow on Friday December 07 2018, @07:00AM
Those far greater distortions are present. And this weird thing doesn't happen twice a day.