Experts said the quake near the Andamans was an aftershock of the 9.0 magnitude quake.
JAKARTA, Indonesia (AP) -- Powerful earthquakes sparked panic in two countries Monday, nearly a month after a quake triggered a deadly wall of water that killed more than 160,000 people, but there was little damage, no reported injuries and no tsunami.
The two quakes, both magnitude 6.3, jangled nerves across the Indian Ocean region hit by the Dec. 26 tsunami.
Panic briefly spread through the streets of the Indian coastal city of Madras after residents felt an earthquake centered in the Bay of Bengal, about 930 miles away, near the Nicobar and Andaman Islands.
Samuel Cherian, the senior police officer in Campbell Bay on the southernmost island in the Andaman archipelago, said he was sitting in his office when he felt "a sudden jolt."
The aftershock was felt in Aceh province on the northern tip of Sumatra, but such tremors have been common in the past month and residents have largely come to ignore them.
Seismologists said the quake near the Andamans was clearly an aftershock of the 9.0 magnitude quake that struck off the coast of Sumatra a month ago. The two lie on the same fault line, said John Bellini, a geophysicist at the U.S. Geological Survey in Golden, Colo.
But a pre-dawn temblor earlier Monday in the Indonesian island of Sulawesi -- nearly 2,000 miles to the east -- was not triggered by the Dec. 26 quake because they lie on different faults, Bellini said.
"It's just part of the normal seismic activity in that part of the world," he said.
Still, the Sulawesi quake, centered about 25 miles south-southwest of the city of Palu, sent thousands of panicked residents running to higher ground.
"They were shouting, 'Water, water' because they feared waves," said Dr. Riri Lamadjido, at the city's Undata Hospital, which received no injured patients as a result of the temblor. About 30 wooden houses and some shops were damaged, police said.
Although volcanoes have a relationship to earthquakes in that they are created by the movement of tectonic plates, experts say the idea that a massive quake will have a longterm effect on Indonesia's famed Krakatoa volcano is doubtful.
Krakatoa, which produced the world's most powerful explosion when it erupted in 1883 and killed an estimated 36,000 people, sits off the other side of Sumatra island from Aceh province.
Adjacent to the volcano is Anak Krakatoa -- "Krakatoa's Child" -- a small volcanic island that formed last century near the 5,905-foot Krakatoa. Anak Krakatoa erupted repeatedly in 1999, spewing volcanic gases and rocks into the air.
"I wouldn't necessarily look for (long-term) activity in volcanoes which can be correlated with this earthquake," said Tony Qamar, Washington state seismologist and research associate professor at the University of Washington.
Qamar said even a large earthquake, such as the one in central Indonesia, has a limited ability to disrupt an entire faultline.
"When an earthquake happens like that, it creates a stress on a fault, but that effect decreases dramatically as you move away," he said.
Volcanoes have their own earthquake activity, but it is caused by molten rock moving underneath the mountain, Qamar said. "Earthquake activity associated with volcanoes usually isn't that significant," he added.
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