FUKUOKA, Japan – A powerful earthquake jolted southern Japanese islands yesterday, killing an elderly woman, injuring 400 people, and triggering landslides.

In a region still jittery from the devastating Indian Ocean quake and tsunami, authorities evacuated half the residents of a tiny island near the epicenter and warned of a tsunami but later canceled the alert.

The magnitude-7.0 temblor, which hit west of Kyushu Island at 10:53 a.m., was centered at an unusually shallow depth of 5.5 miles below the ocean floor, the Japanese Meteorological Agency said. At least one aftershock with a magnitude of 4.2 was recorded.

Minutes after the shaking began, the agency warned of the possibility of a 20-inch tsunami triggered by the seismic activity. Such waves can grow to towering heights as they approach land, and authorities cautioned residents near the water to move to higher ground. But the agency withdrew the warning after about an hour.

“There may be some disturbance of the ocean’s surface, but we aren’t worried about tsunami damage,” said Masahiro Yamamoto of the Meteorological Agency. He predicted strong aftershocks up to magnitude-6 would continue.

On December 26, a magnitude-9.0 quake triggered a massive tsunami that devastated Asian and African coastlines in nearly a dozen nations, killing at least 174,000 people.

The worst damage from yesterday’s quake was nearest to the epicenter, on tiny Genkai island, where the shaking touched off landslides and leveled homes. About 120 Japanese troops flew to the island just west of Kyushu to offer food and medical aid and help evacuate more than 400 of the 850 residents to Kyushu.

Nearby in Fukuoka city, a 75-year-old woman died after a section of a stone wall fell on her, a Fukuoka prefectural government spokesman said on condition of anonymity.

At least 400 were injured by the quake and treated at hospitals, public broadcaster NHK television reported. Most of the injured were in hardest-hit Fukuoka prefecture on western Kyushu, 560 miles southwest of Tokyo. Authorities in Fukuoka confirmed 107 injuries, according to the prefectural government’s Web site. Some were struck by toppling cabinets or shattered glass, or burned by stoves.

A Fukuoka prefectural police spokesman said the initial jolt, which lasted about 30 seconds, made it difficult to stand. Water and gas pipes burst, hundreds of homes reported power outages, and landslides reportedly triggered a safety mechanism that halted local and bullet-train service.

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

“We have had frightened residents coming to the store because their own homes are shaking with every aftershock,” said a manager at a convenience store in Fukuoka city, Shigeru Harada.

Nearly 2,000 residents, including those from Genkai island, evacuated their homes to stay in temporary shelters in Fukuoka for the evening.

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 briefly shook buildings though no damage was reported.

The tremors also set off landslides in parts of Saga and Nagasaki prefectures, near Fukuoka on western Kyushu, NHK reported.

Ten people in Saga were injured, a prefectural government official said.

In Saga’s Okawa city, a 56-year-old man suffered broken bones after trying to jump to safety from the second floor of his home, NHK said. One person was reportedly rescued after being pinned inside a collapsed home.

Located along the Pacific Ocean’s seismically active “Ring of Fire,” Japan is one of the world’s most earthquake prone countries.

It is also one of the best prepared for a major quake. Tough requirements making buildings quake-safe and frequent disaster drills likely kept injuries and structural damage to a minimum in yesterday’s temblor.

On October 23, a magnitude-6.8 earthquake struck Niigata, about 160 miles northwest of Tokyo, killing 40 people and damaging more than 6,000 homes. The jolt was the deadliest to hit Japan since 1995, when a magnitude-7.3 quake killed 6,433 people in the western city of Kobe.