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On November 11, 2018, a deep rumble ricocheted around the world, one that humans couldn’t feel but that registered quite clearly on seismometers. A new pre-print paper about the event is now suggesting that it was caused by the largest offshore volcanic event in recorded history.
Originating 30 miles east of the island of Mayotte, near Madagascar, the mid-November signal immediately caught the attention of a disparate group of geoscientists. They subsequently took to Twitter to express their fascination over this mysterious event—one even joked about a “giant prehistoric sea monster.”
If the eruption lasts one year, which is typical for volcanic eruption, the subsidence of Mayotte will exceed 0.1 m which is large but not critical for the inhabitants and infrastructures, and the total volume emitted will exceed 2 km3. Such volcanic event near a coast is the largest ever observed and it may be a major teacher for the understanding of how off-shore volcanoes work.
Although the inferred deflation source is deep, not having the experience of previous similar events, we believe that we cannot rule out the possibility of a collapse above the deflated reservoir. Occurring after one year, and involving just 1% of the erupted volume, the deforming source (20 millions of m3) would be equivalent to a disk of 12 km of diameter subsiding by 0.2 m. Such volume scales with some known sources of tsunami triggered by either earthquakes or landslides.
It wasn't an isolated event, the researchers said; evidence was found of 15 super-eruptions and 20 large calderas.
originally posted by: jadedANDcynical
a reply to: ElectricUniverse
I'm glad you brought this up. I went back and was looking at the spectrogram:
And noticed that in the decay portion of the signature, there is still a fairly significant signal response in the 1-2 hz frequency range. This is mirrored by another response, albeit less intense at the 6-8hz range, and again in the 12-14 hz range, evem less intense than that of the response in the 6-8 hz range.
These particular signatures are similar to what can be seen in volcanic tremor, specifically harmonic tremor. Harmonic tremors are indicative or fluid (usually magma, but sometimes water, and even icebergs) movement.
originally posted by: SeaWorthy
One more in a long line of threats the earth is entering into at this time.
If people stayed aware of each one as they come to light they would not sleep well.
so where is the visual evidence?
Several low frequency tremors(e.g. Tab. 1) have been recorded. The largest one, on November 11(Fig. 9), recorded worldwide, awaked the interest of the seismological community and the media. None of those tremors is triggered by a strong earthquake, but there are earthquakes embedded in all tremors and all start with moderate and high frequency events.