There were no immediate reports of damage or injuries, but the Japan Meteorological Agency announced that a tsunami of up to 1.6 feet (a half meter) may wash into Miyagi Prefecture.
The alert was prompted by a quake that the U.S. Geological Survey measured at 7:23 a.m. Monday Japan time (2223 GMT Sunday) near the east coast of Honshu.
The USGS said the quake was 3.7 miles (5.9 kilometers) deep.
A magnitude-9 quake off Japan's northeast coast on March 11 triggered a tsunami that barreled onshore, triggering a humanitarian disaster that is thought to have killed about 18,000 people.
