Something very odd happened a little before 9:30 on November 11, 2018. A seismic wave was picked up by instruments around the world. The ground zero point originated near the shores of the French island of Mayotte, off the coast of Southeast Africa.

This bizarre wave began rolling off of Mayotte and continued to travel for nearly 11,000 miles. It flew over vast oceans, hovered past Chile, New Zealand, and Canada, and even made its way  to Hawaii.

Seismic waves are often detected by the instruments and these vibrations are not really strange.  They are often unexpected, but completely normal.

What really made this seismic wave bizarre is the fact that no one saw or felt it and only one person was able to observe the signal on the US Geological Survey’s real-time seismogram displays. And as the world was busy doing other things, this one earthquake buff was paying attention to the real-time readings and happened to take pictures of the zigzags. When the picture of the waves was posted on Twitter with the caption, “This is a most odd and unusual seismic signal. Recorded at Kilima Mbogo, Kenya …” it gained national and international attention. Subsequently, seismologists from all over the world began to analyze this strange phenomenon.

To make sense of what happened on this day, we first need to understand how seismograms function.

How Does a Seismogram Work?

Seismograms were drawn on a piece of paper through drum recorders 30 years ago. The roll of paper was wrapped around these drums and just when the drum revolved, the pen changed its position and left traces across the paper.

Seismograms were drawn on a piece of paper through drum recorders 30 years ago. The roll of paper was wrapped around these drums and just when the drum revolved, the pen changed its position and left traces across the paper.

Today, the display is digital and records about 100 samples per second.

As soon as an earthquake occurs, a seismograph will display its motions as well as its time. They typically last from seconds to minutes. The height of the seismogram shows the actual ground motion. As a result, the kind of waves that would develop will also show on the seismogram. It could be a P or S. P indicates fastest traveling waves, whereas S indicates shear waves.

That said, earthquake vibrations aren’t the only thing that is caught on the seismogram. If a seismogram is placed too close to the road, it will detect the vibrations caused by all the upcoming cars.  

The only way seismologists are able to tell which waves are an indication of an earthquake is through fluctuating patterns. Ones that show an earthquake are usually spiky and sudden.  

Theories

• Earthquake

Anthony Lomax, an independent seismologist, shared his theory, “the event is almost certainly volcanic-related since Mayotte and the region around is volcanic. The seismic waves may be from earthquake-like, faulting rock movement responding to inflation/deflation or collapse of a volcanic edifice, or directly related to movement or vibration of magma.” 

Again, comes the question, why was it so weird then?  

The signals were noted to be very strange with their long and monochromatic lines, according to Lomax Goran Ekstorm, a seismologist at Columbia University, while explaining the situation to National Geographic said that it was pretty straightforward.  

“I don’t think I’ve seen anything like it [but] it doesn’t mean that, in the end, the cause of them is that exotic,” Ekstorm said.

According to him, these waves began as a result of an earthquake, yet it passed by stealthily without anyone noticing it because it was a very slow earthquake.  

This theory is also supported by the fact that the French island Mayotte is actually part of an archipelago called Comoro, and the islands belonging to this group are identified as volcanic.

Additionally, Mayotte itself is home to two volcanoes that have stayed dormant for more than 4000 years.

National Geographic did some more digging and stated that this island has already experienced hundreds of tremors since May last year.  

The tremor has certainly caught the attention of the experts and the authorities.  The French Geological Survey has become highly active in the area to monitor the zone for any new volcanic activity.

Based on their examination, The French Geological Survey put forward the theory that these waves might be an indication of a mass movement of magma underneath the earth’s crust, referred to as chamber collapse.

The collapse is mostly triggered when the magma chamber beneath the volcano empties because of a large volcanic eruption. This eruption could be a singular event, or it could be a series of eruptions.  

• Nuclear Tests

There were many online theorists who did not share Ekstorm and Lomax’s views. Their theory is based on the probability that traditional earthquakes send a jolt of high frequency waves, and that is how it is seen on the seismogram. On the other hand, this reading from November 11 picked up low yet consistent waves that lasted for more than 20 minutes.

If the effects of these were really felt, it almost would have felt like as if the earth rang like a bell.

Not yet ready to cast this off as earthquake-related waves, online theorists suggested that these waves might be a result of covert nuclear tests.

• Other Theories

Since the pictures went public, netizens began to come up with their own theories.

Some suggested sea monsters, humongous ones. Others also suggested a meteorite that could have caused this rumbling tremor seen on the seismogram.

Helen Robinson, a Ph.D. candidate in applied volcanology at the University of Glasgow, also agrees with the first theory, believing that it could be a result of the complex geology of Mayotte that caused these strange waves.

However, talking to National Geographic, she also said. “It is very difficult, really, to say what the cause is and whether anyone’s theories are correct—whether even what I’m saying has any relevance to the outcome of what’s going on.”