Core-bounced seismic echo nudges Japan 6 mm after 2011 megaquake, study finds
A 2011 magnitude-9 earthquake off northeastern Japan generated an unusually strong ScS wave that travelled down to about 2,890 km, reflected off the outer core, and returned to the surface 13 minutes later, prompting a near-simultaneous 5–6 mm eastward shift across Japan and likely triggering tiny slip on stressed faults. This is the first observation of a core-reflected wave delivering measurable surface motion, with implications for how giant earthquakes are modeled for seismic hazard.
