Magnitude 5.1 and 4.7 quakes have struck Ibaraki Prefecture back to back. The Japan Meteorological Agency says there is no threat of tsunami.
The agency says the second and stronger quake occurred at 0:50 a.m. on Monday. The agency estimates the epicenter was in northern Ibaraki, and the focus was at a depth of 8 kilometers.
In Hitachi city, Ibaraki Prefecture, the quake had an intensity of lower 5 on the Japanese scale of zero to 7.
The agency adds that two minutes earlier, at 0:48 a.m., the magnitude 4.7 quake occurred in northern Ibaraki. The focus was at a depth of 10 kilometers. The quake had an intensity of 4 in the cities of Hitachi and Takahagi both in Ibaraki.