Aftershocks have been recorded for both earthquakes. On Dec. 8, Japanese authorities warned an even more powerful earthquake could strike within the next week and called on residents from the northernmost island of Hokkaido down to Chiba prefecture, east of Tokyo, to be on high alert.

Another 6.7-magnitude earthquake hit Japan on Friday (December 12), just days after a powerful 7.5-magnitude quake struck the same region and left at least 50 people injured.

The Japan Meteorological Agency has released a tsunami advisory for the Pacific coastline in northern Japan.