Survivors use hands in rescue dig
Aid workers are finding those affected live in inaccessible areas.
Death toll is likely to rise from earthquake near Sumatra.
Scientists try to find out why two quakes had such different results.
(CNN) -- Survivors of the great earthquake that struck off Sumatra have used their hands to dig through rubble while searching for loved ones on the hard-hit Indonesian island of Nias.
The scene in the main town of Gunungsitoli was one of destruction, with numerous buildings in the city's commercial district have been flattened.
The coastal road linking the town with the airport 12 miles (19 km) away was impassable due to a landslide that sent massive boulders cascading down on to the road.
The airport runway was also damaged, although it was open to light traffic.
Indonesian troops could be seen guarding official buildings in Gunungsitoli, but the overwhelming impression on the island was one in need of shelter, earth-moving equipment and emergency medical support.
In some areas of Gunungsitoli, survivors used their hands to sift through rubble in the absence of large equipment.
Many people slept in churches and mosques overnight, but most residents opted to sleep outside in the rain, rather than inside, CNN's Hugh Riminton reported from the scene.
Indonesian authorities have said 230 people were killed on Nias and another 100 died on nearby Simeulue Island. The death toll is expected to rise.
Sumatra Governor Rizal Nurdin estimated the death toll had risen to 1,000, while government officials have said it could climb as high as 2,000, The Associated Press reported.
Dino Patti Djalal, an Indonesian government spokesman, said about 150 buildings have collapsed.
"Many of the victims have fled to the hills they are so traumatized. Many have not returned to their homes yet," he said.
He said they are in most need of food, medicine and heavy equipment.
"Any medical teams would be helpful. We are already also employing the assistance of friendly countries to help the victims."
Luck a factor
A geologist said Tuesday that it was luck that spared southern Asia from widespread devastation like the one last year.
Monday's quake, measured at 8.7 by the U.S. Geological Survey and 8.5 by the Pacific Tsunami Warning Center, sparked region-wide fears of a replay of the more powerful earthquake that hit the same region December 26, setting off a tsunami that left more than 300,000 people dead or still missing. (Full story)
The absence of an early warning system in the Indian Ocean has been decried as contributing to the large death toll. (Full story)
On Monday, local and national governments issued tsunami warnings and ordered evacuations of coastal areas, but soon canceled the alerts.
In Sydney, Australian Prime Minister John Howard said he is sending military transport aircraft and a supply ship to Indonesia to help the earthquake relief effort there. Full story
Howard said he offered medical facilities and emergency aid to Indonesian President Susilo Bambang Yudhoyono during a telephone call Tuesday.
U.S. President George W. Bush offered condolences to the victims of the earthquake and said American officials had offered assistance and were ready to provide it where needed.
"This earthquake has claimed lives and destroyed buildings in a part of Indonesia that is only now beginning to recover from the destruction caused by the tsunami three months ago," Bush said.
Monday's earthquake was smaller than the prior great quake, and the earth ruptured in a different direction, said Patrick Leahy of the U.S. Geological Survey.
"The quake yesterday, the rupture moved to the southeast," Leahy told CNN's "American Morning."
"So it ruptured in the opposite direction."
Though the earth moved along the same fault that moved in December, a number of factors mitigated the impact, including the change in direction and the depth of the water, Leahy said.
"I believe we were lucky," he said. "Certainly the setting -- the so-called subduction zone earthquakes where the earth's tectonic plates are grinding against one another and actually one is sliding under the other -- is the typical place where one would get great earthquakes and ones that would create tsunamis." (Full story)
The December 26 quake -- measured at 9.3 by the PTWC and 9.0 by the USGS -- and the tsunami it spawned caused massive damage around the Indian Ocean basin.
Monday's event marked the first time in recorded seismic history -- more than a century -- that two quakes of such size have happened so close together, said Kerry Sieh, a professor of geology at the California Institute of Technology.
Only 12 great earthquakes have occurred since 1906, he said.
Though Monday's quake and last December's quake were both classified as "great," the most powerful of seven levels on an open-ended scale, the latest was about a third as powerful as the December quake.
CNN's Geoff Hiscock contributed to this story from Sydney