Japan Shifted East by Earthquake Waves

The 2011 Tohoku earthquake, a magnitude 9.0 event, triggered a surprising eastward shift in Japan, moving the country by up to 6 millimeters relative to distant points. Researchers have discovered that seismic waves, after reflecting off the Earth's core, may have reduced friction on fault zones. This reduction in friction, combined with the powerful earthquake waves, is suspected to be the cause of the sudden eastward displacement.

The affected rupture zone was enormous, stretching approximately 3,000 kilometers, making it the largest recorded from a single earthquake. This finding suggests a previously unrecognized seismic hazard where fault zones can become reactivated minutes after a mainshock. The study, published in the journal Science, analyzed data from Japan's Geonet earth observation system and global navigation satellite systems.

The consequences of the 2011 event were devastating, including a massive tsunami and the Fukushima Daiichi nuclear disaster. This new understanding of the earthquake's impact on Japan's geographical position adds another layer to the event's complex aftermath and implications for future seismic hazard assessments.