Foreign Minister Alexander Downer said Australian aid workers were already in the region and could be deployed to the worst-hit island of Nias at short notice.
Downer said Australia could also provide emergency relief supplies but was awaiting damage assessments from Indonesian authorities to determine what level of aid response was required.
"We are very willing to provide Indonesia with significant assistance if it is necessary," Downer told reporters.
The Australian government pledged one billion dollars (770 million US) in aid and loan packages to Indonesia after the December 26 tsunami disaster, in the country's largest ever humanitarian assistance project.
The Red Cross, which received more than 100 million dollars in tsunami-relief donations from the Australian public after the December quake, said it was sending a plane and helicopter to assess damage to the Sumatran coast.
"At this time we are concerned about the coastal islands where initial reports say there has been some damage, injuries and possibly even some casualties," Australian Red Cross chief Robert Tickner said.
Tickner said the Red Cross had already identified Nias as a priority for major infrastructure rebuilding after the December disaster, with plans to build up to 500 new houses on the island.
He said the charity was confident it has enough relief stock, vehicles and emergency staff on the ground in the disaster zone to respond to the needs of the coastal communities affected by the earthquake.
Indonesian authorities say the quake, measuring 8.7 on the Richter scale, could have killed up to 2,000 people on Nias.
The undersea eruption was almost as big as the December 26 quake, a 9.0 on the Richter Scale, but did not generate the massive tsunamis that killed more than 273,000 people, some 220,000 of them Indonesian.