Japan Ends Advisory After M7.7 Quake Off Northeastern Coast — Earthquakes Today
Japan’s weather agency ended a weeklong advisory on earthquakes today after an M7.7 temblor struck off northeastern Japan and shook a wide stretch from Hokkaido to Chiba. The advisory had told residents in seven prefectures to keep up “special” readiness until 5 p.m. Monday.
The advisory system, known as the Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory, was issued a few hours after a magnitude 7.7 quake rattled Aomori Prefecture and its vicinity at 4:52 p.m. on April 20. That quake sent a tsunami as high as 80 centimeters to Kuji Port in Iwate Prefecture, and the Japan Meteorological Agency said it would not issue a new advisory after ending the alert Monday.
Japan Meteorological Agency and the April 20 quake
The Japan Meteorological Agency said it believes the April 20 quake and the latest Monday quake were not directly related. The latest quake struck the Tokachi region of northern Japan at 5:23 a.m. Monday and registered upper 5 on Japan’s seismic intensity scale of 7 in the town of Urahoro, with its focus at a depth of 83 kilometers.
The agency’s warning system is meant to flag a relatively higher possibility of large earthquakes along the Japan and Chishima trenches. It drew on lessons from the M9.0 megaquake that devastated northeastern Japan on March 11, 2011, and the M7.3 temblor that followed.
Hokkaido, Aomori and Iwate
In Hokkaido, a woman in her 90s living in a facility in Hakodate was slightly injured when she fell. The total number of injuries in Hokkaido, Aomori and Iwate prefectures reached 10, and more than 100 schools in those three prefectures were temporarily closed.
The Hokkaido Shinkansen bullet train service was not disrupted. Japan says the advisory covered seven prefectures from Hokkaido to Chiba, so the end of the warning returned responsibility to local residents and institutions that had been operating under the heightened-readiness notice.
Japan’s trench warning system
Japan estimates that up to 199,000 people could die in a worst-case quake along the Japan and Chishima trenches, and Japan says tsunami waves could reach nearly 30 meters in some areas. Japan also says fatalities could be reduced by 80 percent through enhanced evacuation measures.
For people across the seven prefectures, Monday’s decision removes the specific advisory that had called for “special” readiness, but the practical issue now is how quickly schools, transport operators and facilities reset their procedures after a week of heightened alert.
