New scientific research regarding the powerful 2011 Tohoku earthquake in Japan has revealed striking findings about the event's long-term geological impact.
Operative Information Center-OMM reports, citing international media, that the study sheds new light on the mechanics of the disaster.
Scientists have determined that a powerful seismic wave, which traveled deep into the Earth's interior before returning to the surface, triggered tectonic plate movement, causing Japan to shift permanently eastward. The Tohoku earthquake occurred when the Pacific Plate suddenly slid beneath the plate carrying Northern Japan, marking it as one of the most powerful seismic events in recorded history.
An international research team led by seismologist Sunyoung Park of the University of Chicago determined that one of the seismic waves generated by the earthquake descended to the boundary between the Earth's mantle and the liquid outer core.
This powerful shear wave, which scientists refer to as "ScS," struck the core boundary and returned to the Earth's surface, where it was recorded with extraordinary precision by Japan's advanced geological observation network. Researchers noted that the wave's impact was so significant that it was clearly observed not only by traditional seismometers but also by GPS stations monitoring surface movement, with signals even detected by observation stations in China.
The study provides deeper insight into how processes occurring in the Earth's deep layers can influence tectonic movements on the surface.
Under normal conditions, the Earth's surface is expected to return to its previous state after a seismic wave passes. However, researchers found that at the moment the reflected wave reached Japan, some GPS stations shifted 5-6 millimeters eastward compared to their initial positions. After ruling out data errors or underwater landslides, computer modeling confirmed that this permanent displacement was caused by the seismic wave returning from the core boundary, which exerted additional pressure on the contact zone of two tectonic plates already under high stress from the main earthquake.
Although the reflected wave was significantly weaker than the main shock, its synchronous arrival across a vast area of Japan facilitated small-scale slippage along plate boundaries.
This phenomenon, observed for the first time in the scientific community, did not manifest as a separate earthquake on the surface because it spread along a massive plate boundary rather than creating a single large rupture. Experts estimate that this large-scale, millimeter-level slippage was equivalent to a magnitude 7.5 earthquake in terms of total energy. Researchers emphasize that further observation and analysis of future major earthquakes using similar methods are essential to fully confirm this mechanism.
