Unlike the massive 9.0 magnitude earthquake that killed hundreds of thousands last December, Monday night's 8.7 earthquake spawned no tsunami waves of destruction. But for government officials, this week's powerful quake - among 10 of the strongest ever recorded - was a crucial test of the early warning systems they have in place, and one that exposed serious flaws.
Among the countries with quicker responses were Thailand and Sri Lanka. Thai police with loudspeakers fanned out to order thousands of residents and tourists to evacuate.
Slower on the draw were India and Indonesia. India's tsunami warning came at 11:30 p.m., nearly two hours after the quake. In Indonesia, thousands of coastal residents didn't wait for government warnings. They felt the quake and fled.
Compared with the Dec. 26 disaster, the death toll from this latest temblor was relatively low - anywhere from 300 to 2,000 predicted deaths, most of them concentrated at Indonesia's Nias Island. Citizens tempered by experience quickly sought safety. And relief efforts from the first quake seem unaffected thus far.
But the quake may serve as a prod for Indian Ocean nations to speed up their response times, and to create a unified early warning system like the multination system that operates in the Pacific Ocean.
"It's frustrating that with all the seismic networks that give us such good information, we still don't have the capability to quickly determine" the passing of tsunamis," says Costas Synolakis, director of the Tsunami Research Center at the University of Southern California.
"What we do know is that people acted as their own tsunami warning system once they felt the earthquake," and headed for high ground, says Art Lerner-Lam, with the Lamont-Doherty Earth Observatory in Palisades, N.Y.
For residents of Indonesia's Nias Island, just 19 miles from the epicenter, there wasn't time to respond. Local officials say that the two-minute-long quake destroyed nearly 80 percent of the island's buildings, trapping or killing residents.
But elsewhere, Indonesians knew to seek higher ground, even without warnings. Foreign-aid workers say that the roads of Aceh's capital city of Banda quickly jammed with vehicles heading inland. Thousands of residents spent the night outdoors, as 12 major aftershocks followed the first massive quake at 11:09 p.m. Indonesian time.
"It was absolutely surreal," says Paul Dillon, spokesman for the International Organization for Migration in Banda Aceh. "We ran outside to see these ancient huge trees swaying in the middle of the trunk. Electrical towers were swaying back and forth like a picket fence on a windy day."
UN agencies and aid groups, who were already in the region and able to move quickly, mobilized helicopters and truck convoys to send food, medical supplies, and tents to Nias Island. The supplies were not diverted from current relief efforts. "We always maintain emergency supplies, so we are reverting to emergency stocks to meet the need in Nias," says Michele Lipner, head of the UN Office for the Coordination of Humanitarian Assistance in Banda.
Officials with the government's disaster-management task force said that there was still no fully functioning tsunami early-warning alert system like that in the Eastern Pacific. The UN estimates a similar system will be in place by 2006.
Indonesian Information Minister Sofyan Djalil said Tuesday that the government was still planning a response after an emergency meeting and dispatching two ministers to Nias. Communications to Nias were still "very difficult," and that officials were waiting for police and military reports.
Indonesian officials say that the latest quake has not changed the master plan for rebuilding in Aceh where fresh damage appears to be light.
Thailand has already begun installing early-warning towers along Phuket's beaches. The towers link to a national disaster center and are designed to relay information to radio and TV stations and send text messages to Thailand's 20 million mobile-phone users. Towers in Patong Beach in Phuket, the first to be installed, broadcast a warning on Monday night that was heard at least a mile away.
Even without this system fully in place, Thailand issued a tsunami warning about 30 minutes after the quake. Police with loudspeakers fanned out along the resorts to order tourists and residents to evacuate. A flurry of phone calls and text messages sent a tremor of panic.
Low-tech methods also proved useful in spreading the word, says Alisdair Forbes, managing editor of the Phuket Gazette. "People were telling each other and banging on doors.... It worked pretty well, even though the warning system isn't yet in place," he says.
Radio and TV stations played their part in relaying the warning issued to six provinces along the Andaman coast, where the Dec. 26 tsunami landed. This contrasts with the tardy response by networks on Dec. 26, when programmers were reluctant to break from schedules to cover the deadly impact.
Mobile-phone networks jammed in Phuket and roads snarled with fleeing traffic. Some of those that fled were slow to return, even though Thailand gave the all-clear within four hours. Officials say the congestion shows the need for designated safe spots that can be reached on foot.
A Thai official assigned to oversee the warning system said response was encouraging. "We did a better job than the last tsunami, but it wasn't perfect," says Smith Thammasaroj. He said it would take six months to install warning towers across six tsunami-affected coastal provinces.
Prime Minister Thaksin Shinawatra said Tuesday that Thailand would roll out its preliminary warning system "because we do not want to wait for other countries any longer."
Smith said there was no attempt to coordinate the response on Monday among Indian Ocean nations to the tsunami threat, and said the UN should designate a country to take a lead in future.
In India's Andaman and Nicobar Islands, thousands fled before a tsunami warning. The state of Tamil Nadu received an alert Monday night, and asked fishermen to move.
Yet while re-sponse was comparatively slow, it was faster than on Dec. 26. Then, the Indian Crisis Management Group didn't meet until six hours after the quake.
• Contributors: Simon Montlake in Bangkok, Tom McCawley in Jakarta, and Peter N. Spotts in Boston.
Monday's 8.7 earthquake struck some 100 miles southeast of where December's earthquake began. The area has a history of major quakes. It embraces a region where three large plates and one "micro" plate in the earth's crust meet in a jumble of crust-grinding boundaries.
This week's temblor occurred along the boundary between the Australian and Sunda plates and ruptured to the south. The segment was responsible for a magnitude 8.5 earthquake in 1861, which produced a tsunami.
In the March 17 edition of Nature, researchers at the University of Ulster in northern Ireland, noted that subduction-zone quakes (produced by one plate sliding under another) often trigger additional quakes. The group noted that offshore fault zones to the south were likely to see a buildup in stress "over the months ahead." But they pointed to the Sumatra fault, which runs up the island's spine, as the "greatest immediate threat."
Despite the quake's intensity, the region dodged a bullet for tsunamis. Based on current information, experts cannot really determine why such a large quake did not generate a sizable tsunami. Tide gauges in the Maldives and the Cocos Islands registered tsunamis from 2 to 9 inches high, according to the Pacific Tsunami Warning Center in Hawaii.
Since tsunamis move outward perpendicular to a fault, the orientation of the fault in this quake appears to have sent the wave southwest into the open Indian Ocean and eventually to Antarctica.
Indeed, preliminary modeling results from the US National Oceanic and Atmospheric Administration indicates the tsunami headed in this harmless direction. It had in its path a channel between two large islands. When the tsunami passed through, the wave may have lost much of its focus, suggests Costas Synolakis, director of the Tsunami Research Center at the University of Southern California.
But the region still lacks a network of ocean sensors to detect these waves. Five hours after the quake, researchers were struggling to characterize the hazard. "It's like we're in the stone age," Dr. Synolakis says, describing frantic phone calls to see if a tsunami had hit in certain areas.
- Peter N. Spotts