A series of earthquakes with magnitudes of 7 or 8 may occur after a 7.5 magnitude quake struck off the east coast of Aomori Prefecture on Monday, a research institute has said.

Fumiaki Tomita, associate professor at the International Research Institute of Disaster Science of Japan¡¯s Tohoku University, called on people to remain prepared for possible major quakes and tsunamis even after the Japan Meteorological Agency¡¯s warning for a possible subsequent huge earthquake, which was issued soon after the Monday quake, ends at 11:59 p.m. next Monday.

The warning was issued for residents of the Pacific coastal areas from Hokkaido to Chiba Prefecture. Monday¡¯s quake registered up to upper 6, the second-strongest level on Japan¡¯s seismic intensity scale.