Seismic sensors on an island between Madagascar and Africa first picked up the occurrence. Then, alarms started to go off as far away as Chile, New Zealand, and Canada.
On November 11, 2018, the "event," which
lasted for around 20 minutes, was also reported in Hawaii, which is almost
precisely on the other half of the planet. No one is aware of what it was.
Meteorite? Underwater volcano? atomic explosion?
Seismologist Göran Ekström from Columbia University is quoted by National Geographic as saying, "I don't think I've seen anything like it." It doesn't imply that their underlying cause is particularly unusual, though.
At the center of the mystery is the little island of Mayotte, which is situated roughly halfway between Africa and Madagascar. It has seen a wave of earthquakes since May. The majority have been minor, but the largest, which occurred on May 8, was the biggest earthquake ever recorded on the island, measuring 5.8 on the Richter scale.
When the strange ringing was first noticed in early November, the seismic swarm was, however, in decline. Ekström, a specialist in atypical earthquakes, notes that there were many peculiar aspects to the events of November 11, 2018. The planet seemed to maintain a low-frequency monotone as it grew, sounding like a bell.
By definition, earthquakes are perceived as brief, acute "cracks." Bursts of easily recognizable seismic waves propagate outward from the point of the slippage when pressures in the Earth's crust are unexpectedly released.
The primary wave, or original signal, is made up of
clusters of high-frequency compression waves that radiate outward. The
Secondary wave, which has a greater frequency and is more likely to "wiggle,"
comes next.
Then follow the slow, deep rumbles of the surface waves, which may circle the Earth several times. The occurrence on November 11 is notable for not having any significant or auxiliary waves. A deep, resonant surface wave was the only thing that was audible. It also didn't tremble like the surface wave of an earthquake. Instead, it maintained a frequency that was considerably crisper and almost musical.
The French Geological Survey thinks a new volcano is erupting off the coast of Mayotte, according to National Geographic. Although the volcano has been dormant for almost 4,000 years, it was the volcanic activity that created the island.
The French believe that the odd ringing was brought on by magma activity that occurred 30 miles offshore and deep underground. In less than five months, Mayotte had moved 2 inches to the southeast, according to GPS sensors. It is, nevertheless, a poorly mapped region. It is difficult to know everything that exists beneath the water.
Ekström hypothesizes that magma churning inside a
chamber or being pushed through a breach in underlying strata produced the
incredibly clean signal.
But he is uncertain.
Reference(s): National Geographic
No comments