Japan has "moved"

At least one reflected seismic wave traveled about 2,900 kilometers during the magnitude 9.0 earthquake that struck Japan in 2011. According to analyses of GPS data, the wave played a key role in triggering additional seismic processes, reports Science Alert.

This event represents the first documented case of a seismic wave reflected from the core-mantle boundary causing additional fault slip.

While analyzing the data, scientists observed an unusually clear ScS signal in the GEONET GNSS network. A ScS wave is a seismic wave that reflects off the core-mantle boundary.

Although GNSS systems measure ground movement rather than seismic waves directly, the signal was so strong that it was detected even in China.

Further research showed that individual GPS stations did not return to their original positions after the wave passed. Instead, they recorded a small but permanent displacement, ruling out the possibility of a data-processing error or other known geological processes.

Models developed by the researchers indicate that the reflected seismic wave may have triggered a slight slip along already stressed tectonic plate boundaries, resulting in several millimeters of surface movement.

On March 11, 2011, a magnitude 9.0 earthquake struck the northeastern coast of Honshu, Japan's largest island. Lasting approximately six minutes, it remains the strongest earthquake ever recorded in the country's history.

The earthquake was caused by the subduction of the Pacific Plate beneath the Okhotsk Plate, which led to the rupture of a fault zone approximately 300 kilometers long and significant ground displacement.

The earthquake generated a devastating tsunami, with waves reaching up to 40 meters high. The tsunami penetrated as far as 10 kilometers inland, devastating many coastal communities.

It also triggered the Fukushima nuclear disaster after flooding disabled the cooling systems of several reactors, leading to reactor failures and large-scale evacuations.

According to official estimates, approximately 20,000 people died or were reported missing, while total economic losses exceeded $150 billion.