An earthquake with a preliminary magnitude of 6.8 jolted the Pacific side of Hokkaido and northeastern Japan regions Wednesday evening, followed by another quake with a preliminary magnitude of 6.1 that rocked Ibaraki, Chiba and other areas in the Kanto region, according to Japan News Agency (Kyodo). The quake registered 4 on the Japanese seismic intensity scale of 7 in the Kushiro area of southeastern Hokkaido and in parts of Aomori and Iwate prefectures, while the temblor logged upper 5 in some areas of Ibaraki and Chiba prefectures. A series of aftershocks recording up to 3 on the Japan scale followed the strong quakes, the agency said, calling for the public to stay alert for aftershocks of up to 4 within a week or so near the areas hit by the second temblor.