Curated by RSF Research Staff
Unusual Seismic Phenomenon heard around the World
A “Mystery Signal” puzzles seismologists, as it was unprecedented in the records. In a National Geographic Article from 28th Nov. 2018 a couple of seismologic Experts discussed a global Phenomenon on 11th Nov 2018 just before 9:30(UT), that has emerged from the ancient African seismic activity zone at the Mayotte Islands located between Africa and the northern Tip of Madagascar. It was first discovered and posted on Twitter by an earthquake enthusiast with the handle @matarikipax, who was monitoring U.S. Geological Survey's real-time seismogram displays.
The coherent waves propagated and were detected across Africa, throughout even Chile, Kanada, Hawaii and New Zealand over a period of 20 minutes. However, National Geographic states, “it seems, no human has felt them”…
I don't think I've seen anything like it. [...] Yet many features of the waves are remarkably weird—from their surprisingly monotone, low-frequency “ring” to their global spread [, …] researchers are still chasing down the geologic conundrum.
Stephen Hicks, a seismologist at the University of Southampton published the global seismic graph on this event on his Twitter shown above. He explains, these waves are in an earthquake usually companioned by High-Frequency “wave trains”. However, these were not what was seen in the „11/11 Mayotte-Event”, which had a seemingly coherent Low-Frequency wave with a 17-second wave period, as reported by National Geographic, another Source states it’s been a 16-second period.
So, was it the whole Globe vibrating like a huge Bell of Freedom?
It's like a music instrument. […] The notes of a music instrument—whether it's grave or very pitchy—depends on the size of the instrument.
The signal's odd uniformity could be due, in part, to the surrounding rocks and sediments, Anthony Lomax, an independent seismology consultant adds. Perhaps the local geology is filtering the sounds and only letting this single 17-second wave period escape. “They're too nice; they're too perfect to be nature,” Helen Robinson, from University of Glasgow jokes. “It is very difficult, really, to say what the cause is and whether anyone's theories are correct.” Most current guesses revolve around resonance in a magma chamber, triggered by some type of subsurface shift or chamber collapse, concludes the National Geographic Article. However, every explanation given sounds vague and speculative. Anyway, what the French Geological Survey (BRGM) called the "atypical very low-frequency signal" was a repeating wave, spread around the globe, would register about every 17 seconds and lasted some 20 minutes in total. Rayleigh waves are an interesting related Phenomenon, which is also observable in crystal material, as discussed by Prof. Oliver B. Wright, Assoc. Prof. Osamu Matsuda from Laboratory of Applied Solid State Physics, Research Group of Quantum Matter Physics, Hokkaido University. Further Observation on this Topic is needed and Future Research on it will be monitored.
Author: Dr. Johanna Deinert, MD, RSF Research Scientist
Articles: National Geographic, Weather.com
Rayleigh Waves related Website on Watching ripples on crystals by Wright and Matsuda.
Pacific Northwest Seismic Network
Suspicious Observers (YouTube): Mystery Seismic Signal