A magnitude 7.3 earthquake struck northeastern Japan on Saturday night, local time. No tsunami warning was issued. But more than 100 people have been reported injured.
Japan's Meteorological Agency believes this was an aftershock from the massive earthquake that hit the region in 2011.
The agency's Senior Coordinator for Seismological Information, Kamaya Noriko, said, "There is a growing risk of houses collapsing and landslides in areas that were hit hard by the quake. People are advised to be on the alert for quakes with a maximum intensity of six-plus for the next week or so."
The large quake on Saturday night was followed by a series of jolts coming from off the coast of Fukushima Prefecture. Officials are calling on people to remain on the alert for further aftershocks.
The initial quake registered a six-plus on the Japanese scale of zero to seven in four municipalities in Miyagi and Fukushima prefectures.
The Meteorological Agency believes the focus was off the coast of Fukushima Prefecture, at a depth of 55 kilometers.
The Japanese government has sent a survey team to assist officials at Fukushima Prefecture's government office.
Prime Minister Suga Yoshihide said early Sunday morning that there is no danger of a tsunami. He added that nuclear power plants have not reported any problems.