TOKYO (AP) -A powerful earthquake rattled southern Japanese today, swaying buildings and prompting warnings of tsunami. There were no reports of damage or injuries.

The magnitude-7 temblor, which hit west of Kyushu Island at 10:53 a.m., was centered at an “extremely shallow” depth below the ocean floor, the Meteorological Agency said. An hour after the initial temblor, aftershocks followed – at least one a magnitude-4.2 quake. An hour after the initial quake, the agency said the tsunami danger had passed.

Officials reported water main breaks, and the possibility of power blackouts.

Local and bullet train railway service was halted, after an automatic safety mechanism was triggered by the tremors, NHK reported.

Local officials in the southern state of Fukuoka, about 562 miles southwest of Tokyo, told NHK that the shaking, which lasted as long as 30 seconds, toppled desks and knocked books off shelves and made it difficult to stand.

NHK showed tall office buildings and street lamps in the center of Fukuoka, nearest the epicenter, shaking violently. In residential areas, cracks appeared in sidewalks and parts of retainer walls flaked off.

Kyushu Island is separated from South Korea by a narrow strait of water, and the quake was felt about 130 miles away in South Korea’s port city of Busan, where it was registered between magnitudes 4 and 6 and briefly shook buildings. No damage was immediately reported, a police spokesman in Busan said.

Located along the Pacific “Ring of Fire,” Japan is one of the world’s most earthquake-prone countries. A magnitude 7 quake can cause tremendous damage in populated areas, either by direct damage or triggering tsunami, which are distinguished from normal coastal surf by their great length and speed.