An earthquake with a preliminary magnitude of 4.3 jolted Niigata, Nagano and Gunma prefectures Saturday afternoon, the Meteorological Agency said.
The 12:35 p.m. quake measured 4 on the Japanese seismic intensity scale of 7 in the Joetsu region of Niigata Prefecture.
No tsunami warning was issued, and there were no immediate reports of injuries. The focus of the quake in the Joetsu region was at a depth of about 20 km.