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posted by martyb on Wednesday December 05 2018, @12:55AM   Printer-friendly
from the I'm-all-shook-up dept.

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.

https://www.independent.co.uk/news/world/earthquake-seismic-waves-mayotte-madagascar-volcanic-activity-science-a8659236.html


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  • (Score: 4, Interesting) by HiThere on Wednesday December 05 2018, @05:56PM

    by HiThere (866) Subscriber Badge on Wednesday December 05 2018, @05:56PM (#770184) Journal

    When the ice over land melts, the water runs quickly into the ocean, but it takes multiple thousands of years for the land to rebound due to the removal of weight. Both are happening, but they're happening on different time scales.

    OTOH, most of the current rise in the ocean is due to the oceans getting warmer, and warm water takes up a bit more space than cold water. (This is true while above about 4 degrees Centigrade, when colder water starts expanding to make ice that floats.)

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