AP

Jakarta, Aug 9: A powerful earthquake under the Java Sea shook Indonesia's capital early on Thursday, violently shaking tall buildings and sending panicked residents into the streets.

There were no immediate reports of damage, and geophysicists said there was little risk of a tsunami.

The quake, which struck at 12.04 am (1.04 pm EDT Wednesday) had a preliminary magnitude of 7.5 and was centred about 66 miles east of Jakarta at a depth of 180 miles, the US Geological Survey said.

Residents said tall buildings and single story homes shook violently in the city of 9 million people, and water sloshed from swimming pools.

El-Shinta radio reported that the quake could be felt from Sumatra island in the west to Bali to the east, but that there were no immediate reports of damage.

The quake also was felt in parts of Malaysia, said Don Blakeman, a geophysicist at the USGS National Earthquake Information Centre in Golden, Colorado.

Because of the earthquake's depth, there was little risk of a tsunami, said Robert Cessaro, a geophysicist at the Pacific Tsunami Warning Centre in Hawaii.

None of the instruments closest to the earthquake indicated that a tsunami was triggered, Cessaro said, although he added that there were no instruments "very close" to the quake's epicentre.

The depth of the earthquake "suggests there will be no tsunami," he said.

Cessaro said in order for an earthquake to trigger a tsunami, the quake must rupture the ocean floor with tremendous vertical force, in effect pushing the water upward. The farther away from the ocean floor a tsunami is, the less likely it is to move the water, he said.

The December 26, 2004, earthquake that triggered the tsunami off the coast of Sumatra and killed more than 131,000 in Indonesia's Ache province was just 18 miles in depth, according to the USGS.

Indonesia, the world's largest archipelago, is prone to seismic upheaval due to its location on the so-called Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.