Los big earthquakes They leave terrible consequences: landslides, dead people and heavy losses, among other calamities.
However, although we do not notice it immediately, they are also usually followed by events that cause landslides and ground movementswhich may be related to both the main earthquake and its aftershocks.
And this is what happened with the powerful 9.1 magnitude earthquake that shook Japan he March 11, 2011 at 2:46 p.m., it hit the coast of the island of Honshu and left almost 20,000 dead.
The earthquake triggered a tsunami with giant waves that devastated multiple coastal areas and even flooded the Fukushima nuclear power plant, which almost caused a serious crisis.
Now, scientists surprise with a new discovery: it happens that after suffering from it, the entire Japanese territory moved eastward.
The first recorded case of a wave that sets in motion a fault and moves an entire country
According to an article published in the magazine Science This June 18, 2026, researchers detected that a seismic wave rushed to the Earth’s core and returned to the surface causing a movement that permanently moved Japan about 6 millimeters to the East
As also highlighted in a publication by Science Newsthis is the first recorded case of a reflected wave in the core that sets in motion a fault and moves an entire country.
The study was led by geophysicist Sunyoung Parkfrom the University of Chicago, which highlights a particularity in this case that baffled scientists and that appeared when the phenomenon was still developing.
It happens that 16 minutes after the main earthquake, and before the large aftershocks were recorded, the Japanese GPS stations They detected a jump towards the east which occurred at the same time throughout the country, without being associated with a specific earthquake.
According to the authors’ hypothesis, the explanation was both physical and counterintuitive: the energy of earthquake would have descended through the interior of the planet, impacted in the outer core—a metallic alloy fluid—and bounced back. Already in the crust, this “return” would have reactivated contact zones between plates and produced the millimetric displacement of the archipelago.
«Most of the time we see a displacement like this when there is an earthquake in progress. But there was no known aftershock here at that time, so we were very curious,» the expert explained in a statement.
This is the first time that an S wave reflected from the core is shown to trigger fault slip, Park noted. «It’s a kind of seismic risk that we had not considered before,» he detailed on the subject.
A such a large rupture length is also unprecedented: It is more than twice the rupture length of the 2004 Great Sumatra earthquake.
In the case of the Tohoku earthquake, the landslide caused by the S wave reflected in the nucleus probably It was not noticeablehighlights the article Science News. And he adds that this is because its energy was distributed over a huge surface and occurred relatively slowly, over about three minutes.
The interpretation proposed in the study suggests a direct consequence for the seismic surveillance: A large earthquake may not “end” when the original shaking ends.
«This indicates that large earthquakes can influence the fault even after the main shaking ends. This adds a whole new angle of seismic danger that we didn’t know about before,» Park said.
Finally, researchers warn that future earthquakes may not be as benign.
