There were no immediate reports of damage or injury from any of the quakes, police said. The latter quake was not an aftershock even though the two Hokkaido earthquakes had the same epicenter, the agency said. Quakes of their magnitude can cause widespread damage if they hit populated areas. About 15 minutes after Tuesday's first tremor, a quake of magnitude 4.6 jolted a group of small islands on Japan's southernmost prefecture of Okinawa. There was no concern that the quakes would raise tsunami, or seismic waves caused by undersea disturbances such as earthquakes or volcanic activity.
Japan is one of the world's most earthquake-prone nations.
It sits atop four tectonic plates, slabs of land that move across the earth's surface. Ths website is designed and maintained in cooperation with HelpForMyWebsite.