Magnitude 6.9 earthquake strikes off northern Japan coast, no Tsunami warning issued

Jun 24, 2026

A new study of the devastating 9.0 magnitude earthquake that struck Japan on March 11, 2011, reveals that seismic waves traveled to Earth's core and rebounded to the crust, permanently shifting the entire country eastward by 5 to 6 millimeters. This core-rebounding wave released energy equivalent to a 7.5 magnitude earthquake and activated four major tectonic plates. Researchers suggest this 15-minute round-trip delay could help predict and prepare for delayed seismic hazards.

2011 Japan earthquake displacement

▪The 9.0 magnitude earthquake in Japan on March 11, 2011, caused nearly the entire country to permanently shift eastward by 5 to 6 millimeters.
▪The March 11, 2011 earthquake, which struck 231 miles northeast of Tokyo, triggered a tsunami and a nuclear crisis, killing an estimated 20,000 people.
▪The March 11, 2011 earthquake in Japan caused the island of Honshu to shift eastward by approximately 20 centimeters.

Core-rebounding seismic waves

▪A study led by geophysicist Sunyoung Park found that seismic waves from the March 11, 2011 earthquake traveled to Earth's core and rebounded to the crust.
▪The core-rebounding seismic waves from the March 11, 2011 earthquake released an amount of energy equivalent to a 7.5 magnitude earthquake.

Tectonic plate boundary activation

▪The core-rebounding seismic waves from the March 11, 2011 earthquake displaced four major tectonic plates, encompassing the Pacific, Okhotsk, Philippine Sea, and Eurasian plates.
▪The initial shaking from the March 11, 2011 earthquake may have reactivated the fault around the main quake and triggered movement along distant plate intersections.

Seismic monitoring network capabilities

▪University of Maryland professor Vedran Lekić stated that core-rebounding seismic wave phenomena may occur undocumented in regions lacking adequate instrumentation.
▪Japan's network of seismic and satellite monitoring stations enabled the recording of the core-rebounding seismic wave event from the March 11, 2011 earthquake.

Delayed earthquake hazard prediction

▪The round-trip journey of seismic waves to Earth's core and back takes approximately 15 minutes, presenting a predictable window for potential hazard preparation.
▪Geophysicist Amanda Thomas stated that large earthquakes can continue to influence fault systems through later-arriving seismic waves for many minutes after the main rupture.