BANDA ACEH, Indonesia - Two massive earthquakes triggered back-to-back tsunami warnings for Indonesia on Wednesday, sending panicked residents fleeing to high ground in cars and on the backs of motorcycles.
There were no signs of deadly waves, however, or serious damage, and a watch for much of the Indian Ocean was lifted after a few hours.
Women and children were crying in Aceh province, where memories are still raw of a 2004 tsunami that killed 170,000 people in the province alone. Others screamed "God is great" as they poured from their homes or searched frantically for separated family members.
The U.S. Geological Survey said the first 8.6-magnitude quake was 270 miles (435 kilometers) from Aceh's provincial capital. The tsunami watch that followed from the Pacific Tsunami Warning Center in Hawaii advised countries all along the rim of the Indian Ocean, from Australia and India to as far off as Africa, that a tsunami could be generated.
The only wave, however, was less than 30 inches (80 centimeters) high, rolling to Indonesia's coast.
But just as the region was sighing relief, an 8.2-magnitude aftershock hit.
"We just issued another tsunami warning," Prih Harjadi, from Indonesia's geophysics agency, told TVOne in a live interview.
His countrymen were told to stay clear of western coasts.
Again, the threat quickly passed.
Experts said both quakes were geologically different than the one that spawned the 2004 tsunami, occurring horizontally, with the tectonic plates sliding against each other, creating more of a vibration in the water.
The other type of earthquake, a mega thrust, like the one that also hit off Japan last year, causes the seabed to heave and displaces water vertically, sending towering waves racing toward shores.
Roger Musson, seismologist at the British geological survey who has studied Sumatra's fault lines, said initially he'd been "fearing the worst."
"But as soon as I discovered what type of earthquake it was ... I felt a lot better."
The tremors were felt in neighboring Malaysia, where high-rise buildings shook. Singapore, Thailand, Bangladesh and India also were rattled.
But it was the streets of Aceh where real chaos broke out.
Patients poured out of hospitals, some with drips still attached to their arms. In some places, electricity was briefly cut.
Hours after the temblor, people were still standing outside their homes and offices, afraid to go back inside.
"I was in the shower on the fifth floor of my hotel," Timbang Pangaribuan told El Shinta radio from the city of Medan. "We all ran out. ... We're all standing outside now."
He said one guest was injured when he jumped from a window.
Thailand's National Disaster Warning Center issued an evacuation order in six provinces along the country's west coast, including the tourist destinations of Phuket, Krabi and Phang-Nga.
India's Tsunami Warning Center issued a warning for parts of the eastern Andaman and Nicobar islands. In Tamil Nadu in southern India, police cordoned off the beach and used loudspeakers to warn people to leave the area.
The quake was felt in Dhaka, Bangladesh, where many people in the city's commercial Motijheel district left their offices and homes in panic and ran into the streets. In Male, the capital of the Maldives, buildings were evacuated.
Indonesia straddles a series of fault lines that makes the vast island nation prone to volcanic and seismic activity.
The giant 9.1-magnitude quake and tsunami on Dec. 26, 2004, killed 230,000 people in about a dozen nations.