Is there anything that scientists love more than a mysterious signal? Whether it’s looking for signs of alien megastructures and new planets, or they’ve heard something “whistling” in the Caribbean, unknown blips or echoes are proverbial nectar to these sci-curious folk.
Fortunately, a brand new enigmatic reading has emerged, and already, a team of scientists in Japan think they’ve already cracked the case.
As the new Science study reveals, an extremely elusive deep-Earth tremor has been detected for the first time. These unusual seismic outbursts aren’t like most earthquakes, which happen along fault lines between and along tectonic plate boundaries and which permeate the crust and upper mantle. Deep-Earth tremors were thought to be able to rocket through the deep mantle, and even perhaps reach the core-mantle boundary, which is at a depth of 2,891 kilometers (1,796 miles).
In this case, these seismic waves were picked up by a network of sensitive detection stations in Japan, and the origin point was traced to a spot in the North Atlantic Ocean, somewhere between Greenland and Iceland – and somewhere lacking any earthquake-generating faults or tectonic plate boundaries.
According to a pair of researchers from the University of Tokyo and Tohoku University, it appears a powerful thunderstorm known as a “weather bomb” was responsible. These are small but incredibly potent storms that gain power rapidly as localized air pressure begins to change in an extremely short space of time.
The sea beneath the bomb moved around violently in response to this climatological explosion, and this huge turbulent fluid mass generated pressure waves that traveled through Earth much in the same way that seismic waves from earthquakes do. Although extremely faint by the time they reached Japan, these stealthy waves were captured by the high-tech array of sensors.
As cool as this seismological detective puzzle is all by itself, the detection of these so-called “microseisms” can now also provide researchers with a tool to peer into the hellish depths of our planet like never before.
Gif in text: Imaging the weather bomb (top) and matching it with P-waves emerging on the other side of the world (bottom). P. Gerstoft and J. Zhang
These weather bomb-generated microseisms produced P and S waves, the same types manufactured by earthquakes. P waves move through any type of substance, but S waves, which are slower and arrive after the P waves hit, can only move through solids, not liquids. These waves happen to provide seismologists with remarkable detail as to what the inner structure of Earth looks like.
For example, if an S wave does not travel through an unknown substance at depth, that substance is a liquid, not a solid – and it is this reason they never make it through the liquid outer core. P waves travel more slowly through liquids than solids. Older rock is cooler and therefore more solid than liquid, so the effective age of parts of the partly-molten mantle can be determined using P waves.
All of this information can be used, and has been used, to produce high-resolution maps of Earth’s mantle, which makes up 84 percent of the planet’s volume. It has revealed gargantuan battles between upwelling superheated plumes and collapsing tectonic plates, along with hidden massive molten time bombs under the Pacific Ocean and African continent.
This information is mostly gained from seismic waves generated by earthquakes, but these microseisms produce waves that penetrate to depths rarely touched upon. “The seismic energy traveling from weather bombs through Earth appears to be capable of illuminating the many dark patches of Earth's interior,” the researchers write in their study.
These weather bombs, then, may be about to reveal a great deal about what may be hiding in our planet’s destructive underworld.
How the weather bomb fired seismic waves across the world. K. Nishida and R. Takagi