An earthquake measuring 5.4 on the Richter Scale shook central Japan on Thursday, injuring several people. The quake also caused cracks in a 16th century Samurai castle listed as a national treasure. Seismologists said the quake hit at 8:16 am (local time), some 180 kilometres northwest of Tokyo. It was followed by smaller aftershocks. Television footage showed fallen concrete bricks and roof tiles in the area.