It's highly unusual for earthquakes to reverberate back for a second time, at least that's what experts have thought up until now. We know that tornados can spawn twice in the same place, the hurricanes are technically two-part storms due to the clearing in the eye that passes over, and that lightning does, indeed, strike the same place twice. And now, experts are saying that they've confirmed a "boomerang" earthquake, which has passed through one point and seemingly come back to send tremors through the same area.


Where Did It Happen And When?

The incident scientists are referring to is a location deep within the seabed of the Atlantic Ocean, and no, it didn't happen recently. The earthquake happened during 2016 and while people on land may not have noticed anything unusual, undersea seismometers, as well as monitoring stations, were able to pick up the activity. The fault line, referred to as the fracture zone, according to Science Alert, was roughly 900 kilometers and falls between Africa and Brazil, along the Mid-Atlantic Ridge. The magnitude of the earthquake registered at 7.1, making it significant and causing the equivalent of a sonic boom deep within the seabed.

Related: Can The San Andreas Fault Line Break? And Other Questions, Answered

How Did It Happen?

The earthquake behaved in an unusual way, sending tremors one way before seeming to circle around in a strange pattern to send tremors back the same way. When a fault line shows signs of activity, it's not common for the energy released by the ground to flow back one way and double back, but that's exactly what this earthquake did. Even more disturbing is the fact that when shockwaves were sent back, they moved twice as rapidly. Of the nature of the earthquake, experts are saying, "and unusual back-propagation westwards" occurred, and that the rate at which tremors whipped around and sped back to the center of the fault as "supershear speed."

Related: Marianas Trench Is The Deepest Point On Earth (And That's Not The Strangest Thing About It)

Stephen Hicks, of Imperial College London, said of the activity, "Even though the fault structure seems simple, the way the earthquake grew was not, and this was completely opposite to how we expected the earthquake to look before we started to analyze the data." He also stated that now, according to this new study, scientists finally have proof that such an unusual phenomenon can, and does, occur - and is not simply a theory anymore.

As of right now, there's no solid explanation for how an earthquake such as this occurred. One hypothesis scientists have is that the initial quake released enough energy to trigger a second "rupture reversal," in shallow water according to Science Alert. These types of earthquakes have been researched prior to this point but only now do scientists have the proof they've needed to support their theories. As of right now, this backwards-propagating earthquake is the first one ever to be recorded, but now, at least, it can be studied, and hopefully, in the future, more will be known about these unusual events.

Next: Hawaii's Kilauea Volcano Now Causing Earthquakes, Shooting Rocks Big As Bowling Balls