Abnormal seismic wave recorded on seismographs of various countries. The causes are unknown, doubts also for geologists
A decidedly atypical seismic phenomenon is the one that was recorded during the morning of Sunday 11 November 2018 (at 11.30 am – Italian time). Specifically, we speak of an anomalous seismic wave that has passed through several countries and that has been detected by as many seismographs.
This phenomenon has affected a large part of the globe, which originated – according to the hypotheses and considerations made by National Geographic – about 24 km off the coast of Mayotte, a French island located between Africa and the northern tip of Madagascar.
The seismic waves have spread for about 18 thousand kilometers and, this factor, has allowed to detect this “movement” by the seismographs of many countries.
But the peculiarity of this phenomenon consists in what differs from the traditional earthquakes, which record high frequency pings (the classic zig zag graphics); while, what occurred at Mayotte was a low-frequency signal that has been defined, literally, atypical.
Detection of seismographs
The seismic event that originated off the coast of Mayotte has left many geologists (and others) perplexed. The phenomenon in question generated low frequency waves that usually emanate as a result of a powerful shock; which, instead, didn’t happen in this context, since the event wasn’t preceded by any earthquake. Moreover, according to the seismograph findings, the layout was flat, clean and repeated every 17 seconds for about twenty minutes. This movement seemed to be produced by something artificial (like a drilling of the seabed), but similar activities don’t occur in the circumscribed area mentioned above.
The words of the expert
The expert explains that, in each earthquake, primary, secondary, both high frequency waves are generated, and finally the superficial ones, produced only during the most powerful earthquakes and able to travel even the entire surface of the planet for more times. Sun the last ones, slow and long, turn out to be comparable to those of Mayotte. No strong earthquake struck the area, so the origin of the phenomenon remains a mystery. Small shocks hit the area over the last few months, up to a more intense 5.8 degrees on the Richter scale, and then nothing; until the arrival of these strange seismic waves.
What is the cause that generated this phenomenon?
Bureau de recherches géologiques et minières hypothesises that the anomalous shock is due to the collapse of a magma chamber which, in particular, would have made the magma oscillate inside, thus generating the rhythmic movement of the wave, all connected also to the movement of the archipelago itself. For now, these remain only hypotheses. Only through investigations and more in-depth research can we get to give an answer to this fascinating mystery.
In addition, the French Geological Survey (BRGM) is closely monitoring the tremors in question, from which it deduces and suggests that a new center of volcanic activity could develop off the coast. It’s known that Mayotte was formed by a phenomenon of volcanism but its geological forces haven’t exploded in over 4,000 years. This analysis suggests that this new activity may indicate a magmatic movement offshore, miles away from the coast, hundreds and hundreds of meters underwater. Good news for the inhabitants of the island, a little ‘less for geologists, since the area in question hasn’t been the subject of study. “The position of the swarm is at the limit of the geological maps we have. There are many things we don’t know, “said Nicolas Taillefer, director of the earthquake and volcanic risk unit at BRGM. And as for the waves of November 11, he adds, “it’s something new in the signals of our stations”.
Only with in-depth studies will we be able to get answers. Meanwhile, curiosity pervades us, because we are all eager to know and know the causes.