Updated 6:30 a.m. ET, Aug. 16

A major earthquake with a preliminary magnitude of 7.2 struck offshore, northeast of Tokyo, Japan. It occurred near the east coast of Honshu, 60 miles East of the town of Sendai. [Map]

The quake struck at 11:46 a.m. local time (02:46 Universal Time) on Aug. 16.

The Pacific Tsunami Warning Center issued a bulletin: "No destructive pacific-wide tsunami threat exists based on historical earthquake and tsunami data."

Local tsunami were possible, the center said, but there was only a very minor local fluctuation in sea level.

Early reports put the magnitude at 6.8 to 7.2. But by 8:33 p.m. ET the number had been revised to 7.2 by the U.S. Geological Survey. It could still change as more data rolls in.

Some buildings collapsed and power was knocked out. The temblor shook skyscrapers in Tokyo, more than 300 kilometers (186 miles) away.

A caved-in roof at an indoor pool in the coastal city of Sendai injured 14 people, national broadcaster NHK reported. Two more people were injured in the neighboring prefecture (state) of Iwate, Kyodo News Agency reported.

Footage also showed a collapsed house outside Tokyo and landslides in the quake zone.

The temblor knocked out power to about 17,000 households and suspended bullet train services in northern Japan and temporarily grounded flights at Tokyo's Haneda airport, Kyodo said.

The quake hit around 11:46 a.m. (02:46 GMT) and was centered 20 kilometers (12.4 miles) below the ocean floor about 80 kilometers (49.6 miles) off the coast of Miyagi prefecture (state) in northeastern Japan, the Meteorological Agency said. Two 10 centimeter (4 inch) tsunamis hit the nearby coast shortly after noon, and officials expected little damage from the waves.

The quake was followed by at least four aftershocks and additional quakes of up to magnitude 6 could follow, the agency said.

Authorities in Miyagi prefecture were still assessing damage in the area, local government official Masami Oshima said, adding that it was premature to give estimates.

"The horizontal shaking was very strong, so much so that I almost couldn't remain standing,'' Oshima said.

Sendai, the capital of Miyagi, is about 300 kilometers (186 miles) northeast of Tokyo. A nuclear power plant in the neighboring prefecture (state) of Fukushima was not affected by the earthquake, Kyodo reported citing the plant's operator. Another plant in Onagawa in Miyagi prefecture (state) shut down automatically and was being checked for damage, news reports said.

In 1995, a magnitude-7.3 quake in the western port city of Kobe killed 6,400 people. The depth and offshore location of Tuesday's quake helped limit the damage that might have occurred had it been centered under a city.

Image Gallery

Deadly Earthquakes

Only in California: Daily Earthquake Forecasts

Earth Puts Big Squeeze on Los Angeles

Central US Warned of Larger Earthquakes to Come

Ominous Rumbling Under San Andreas Fault

Seismologists Target Better Earthquake Prediction

Quake Death Toll in 2004 Could Be Worst Since 1556

Earthquakes Stopped, But Only In Lab