MADRAS, India — At a dawn Mass the day after Christmas, as Father Maria Devanesan lifted the host above his head in reverence, the large white wafer began to tremble.

It was 6:30 a.m. in southern India. A tremor had traveled more than 1,000 miles, speeding through the Earth's crust from the seabed off Indonesia to the seashore of India. Now it rattled the pews of St. Thomas Cathedral.

The members of the 500-strong congregation, many of them poor Tamil fishermen and their families who live in shanties at the nearby beach, rose from their knees in fear and ran from the 108-year-old church.

Father Maria hurried down the stone steps from the altar, following his parishioners, who were too afraid to receive Communion. Outside, people rousted from sleep ran from their homes in panic.

When the shaking subsided, the priest persuaded a small group to follow him into the cathedral to pray at the statue of Our Lady of Mylapore, an icon of a woman adorned in gold leaf, joyously anticipating the birth of Christ.

The congregants cried and prayed, thankful that there had been no serious damage from the quake and that the crisis had passed.

In fact, it was just beginning.

The tremor that rattled St. Thomas was merely a knock on the door, a harbinger of a catastrophe that would claim the lives of up to 150,000 people in 11 nations.

Miles beneath the waters of the Indian Ocean, a massive piece of the Earth's crust had heaved, buckled and shifted. Along a fracture zone hundreds of miles long, it moved, releasing pent-up energy equivalent to the power of more than 1,000 atomic bombs. The waters above reared up and crashed down, creating a wave that was now racing across the ocean at 500 mph.

Neither prayers nor science would save those standing in its way.

The records of history and evidence encoded in coral reefs show that tsunamis have hit the Indian Ocean seldom but with great force. At obscure scientific conferences and expert conclaves over the last decade, researchers had urged government officials to establish warning systems. But among the many problems that plague southern Asia — poverty, disease, civil wars — rare but deadly waves seemed a low priority. They were, until the magnitude 9 quake hit.

The cataclysm unfolded over two hours. In that time, some experts around the globe would see the temblor's signature on some of the modern world's most sophisticated monitoring equipment but be blind to the larger threat. Some officials would see the threat, but be ill-equipped to act. Others would take no action for fear of being wrong or out of line. In at least one case — in India — air force officials received a desperate mayday, possibly in time to save thousands of lives, but never made it public.

The wave would outrun them all.

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An Alert in Hawaii

As Father Maria prayed with his congregants, Stuart Weinstein, a 43-year-old former New Yorker now living in Hawaii, was taking advantage of the quiet of a rainy Christmas afternoon to work on a research project.

Inside the computer room of the Pacific Tsunami Warning Center — a high-tech lair of flat-screen monitors, maps and digital wall displays — a computer caught his attention. The jagged lines relayed a signal from a seismic sensor thousands of miles away in the Cocos Islands, southwest of the Indonesian island of Sumatra, conveying the news of a large earthquake off that island's west coast.

The computer automatically sent a pager signal to one of Weinstein's colleagues, Andrew Hirshorn, who had been napping at his home nearby. Hirshorn, a soft-spoken 48-year-old with a gray ponytail, threw on a shirt and ran over.

The two men conferred. Initial readings indicated the earthquake was magnitude 8 — significant, but not enormous. It was outside the Pacific Ocean, their area of expertise and responsibility.

The center, a U.S. government agency that does much of the work for the U.N.-sanctioned Pacific tsunami warning system, was set up in 1965 in response to a quake off the coast of Chile that had generated a tsunami, killing people as far away as Hawaii and Japan. The center monitors sophisticated tidal gauges and computerized buoys dotting the Pacific. Nothing comparable tracks the Indian Ocean.

Computers ate up 15 minutes verifying the earthquake reading, plotting its location, estimating its size. At 3:14 p.m. Hawaii time, the two men sent a bulletin on an automated e-mail and fax list to their colleagues around the Pacific Rim:

TSUNAMI BULLETIN NUMBER 001

PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS

ISSUED AT 0114Z 26 DEC 2004

THIS BULLETIN IS FOR ALL AREAS OF THE PACIFIC BASIN EXCEPT ALASKA-BRITISH COLUMBIA-WASHINGTON-

OREGON-CALIFORNIA.

THIS MESSAGE IS FOR INFORMATION ONLY. THERE IS NO TSUNAMI WARNING OR WATCH IN EFFECT.

AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS.

ORIGIN TIME -- 0059Z 26 DEC 2004.

COORDINATES -- 3.4 NORTH 95.7 EAST

LOCATION -- OFF THE COAST OF NORTHERN SUMATRA

MAGNITUDE -- 8.0

EVALUATION:

THIS EARTHQUAKE IS LOCATED OUTSIDE THE PACIFIC. NO DESTRUCTIVE TSUNAMI THREAT EXISTS BASED ON HISTORICAL EARTHQUAKE AND TSUNAMI DATA.

Already the wave had traveled roughly 100 miles from the epicenter in an ever-widening circle. In Indonesia, the first victims were about to die.

*

'Water! Water!'

What had seemed to be a moderate earthquake shook residents of Banda Aceh, a city of about 150,000 at the northern tip of Sumatra, around 8 a.m. local time. About half an hour later, many of them were outside inspecting their houses for damage when, on what had been a clear, sunny day, the sky filled with water.

Survivors remembered a sound like the drumbeat of a driving rain.

"Water! Water! Big water!" some screamed, unable to articulate the nature of the phenomenon.

This was water like nobody had seen — snarling, tall as a four-story building.

"It was like Armageddon," remembered Zukarnaen Buyung, a strapping 30-year-old construction worker. "We didn't know it was a wave. We thought it was some kind of rain. Everything behind us was black. The sky, the water."

Buyung ran.

Little high ground exists in Banda Aceh, which is built along a palm-studded coastal plain, but Buyung managed to scramble up a bridge, dragging his wife and their 2-year-old daughter.

They watched, horrified, as the strangely voracious water swallowed up relatives and neighbors. A brother and a nephew disappeared as Buyung looked down, helpless.

"I watched. I couldn't do anything," he recalled, his voice choked with grief.

The tsunami obliterated a swath of the city stretching three miles from the sea. It lifted 75-foot fishing boats and dumped them in the middle of the city, deposited hundreds of bodies in front of what had been brightly lighted shops on Panglima Polem Street. Single-story wooden houses were dismantled as if they were made of sticks, and trees were pulled out like blades of grass.

South along Sumatra's long Indian Ocean coastline, entire villages disappeared without a trace.

*

Sucked Out to Sea

At roughly the same time, the wave washed over the Indian air force base on the tiny island of Car Nicobar, northwest of Sumatra.

The base commander later estimated that the wave was 30 to 50 feet high. It killed 102 airmen, sucking the majority out to sea.

Despite the devastation, someone at the base managed to broadcast a mayday on the high-frequency radio. The signal missed its intended military receiver but was picked up at the civilian airport in Madras, on India's southeastern coast, and was relayed by phone to the Tambaram air base, on the outskirts of the city, Group Capt. Anup Ghosh said.

After quickly confirming that the distress call was legitimate and that the airstrip on Car Nicobar still functioned, the air force within 20 minutes launched transport planes to the Andaman Islands, Ghosh said.

But the officers apparently did not alert civilian officials that the wave might be headed across the ocean toward the Indian mainland, about 1,000 miles to the west.

"The initial report was only that the island has been hit by an earthquake and tidal wave," Ghosh said in an interview Friday. "They did not mention tsunami."

Said Squadron Leader Mahesh Upasani, an air force spokesman: "The Indian air force's job is to fight a war and carry out relief operations in such cases, and not to predict tsunamis.

"People were running for their lives," he added. "It was only after some time that they were in a position to communicate."

In a civilian government office in Madras, P. Chandrashekhar Rao was monitoring the seismograph tucked into the corner of a small ground-floor room. He and two colleagues watched the earthquake's impact as the needle bounced wildly across the machine's white cylinder.

The epicenter was hundreds of miles away, and Rao's thoughts quickly turned to the possibility of a tsunami. He did not know enough about the rare phenomenon to make a recommendation. About 10 minutes after reading the seismograph, following official procedures, he called headquarters in New Delhi and reported his findings.

Rao never talked to the air base on the edge of the city, and air force officers there didn't call him. Official channels didn't permit it.

The wave was now roughly an hour from the Indian coast.

*

Growing Magnitude

When an earthquake hits, shock waves travel through the Earth and within minutes begin jiggling sensitive equipment at about 350 monitoring stations around the world. Those stations, in turn, relay data by satellite to computers at the U.S. Geological Survey's National Earthquake Information Center in Golden, Colo.

Don Blakeman, a USGS geophysicist, was about to have Christmas dinner when his pager went off — a computer-generated warning that a major quake had just occurred. A colleague, Julie Martinez, also was paged and began analyzing data on her home computer while Blakeman drove to the office.

As data from more and more stations began to arrive, Blakeman revised the estimate of the temblor's magnitude to 8.5 — a threefold increase in size. He triggered a computer program that notified the White House, State Department and major relief agencies of a massive quake.

The information also went automatically to the tsunami warning center in Hawaii, where director Charles McCreery, 54, had abandoned plans to assemble his young daughters' pink bicycles and joined his colleagues watching the computer readouts.

McCreery saw that the quake was much larger than previously thought and therefore more likely to cause a tsunami. He decided to send out a second bulletin:

NO DESTRUCTIVE TSUNAMI THREAT EXISTS FOR THE PACIFIC BASIN BASED ON HISTORICAL EARTHQUAKE AND TSUNAMI DATA.

THERE IS THE POSSIBILITY OF A TSUNAMI NEAR THE EPICENTER.



Roughly an hour had passed since the quake. Unseen by experts, the wave already had traveled halfway across the Indian Ocean and claimed tens of thousands of lives.

*

Debate in Sri Lanka

The national meteorology department in Colombo, the capital of Sri Lanka, is lined with dusty leather-bound books of weather reports dating back to 1867, complementing a clock that stopped long ago and a calendar stuck on a faraway date. The country is too poor to buy its own seismology equipment and relies heavily on what information can be garnered from abroad.

So when the telephone started ringing off the hook that morning with reports of a tremor, Sarath Premalal, the meteorologist who was nearing the end of his 24-hour shift, turned to the Internet.

Answering the phone with one hand and Web surfing with the other, Premalal found his way to the USGS website. The site reported that the vibrations he had felt were from a temblor centered off western Sumatra.

"Don't worry. It's far away," Premalal told one woman who called from the interior reporting that her building was shaking. "We already know about it."

Despite the reassurance, the meteorologist and his boss, Jayatilaka Banda, the department's deputy director, were concerned about a tsunami. They had never experienced such a thing but knew that underwater earthquakes could generate destructive waves.

Banda thought about asking Sri Lankan radio and television stations to put out an alert to watch for such an occurrence, but he felt he didn't have the authority without credible evidence of a threat. He told Premalal to keep looking for information.

As Blakeman and his colleagues at the USGS boosted their estimates of the quake's magnitude, the two Sri Lankan officials still debated what to do. An hour and 45 minutes after the first tremors, they were still deliberating when an urgent call came from a weather observation office in Trincomalee on the east coast of the country: The town was under 2 feet of water.

Farther north on the island, in territory controlled by Tamil rebels, when the first wave came, Suppaiya Raja, 38, recalled having heard Christian missionaries predict the end of the world in 2005.

"I heard a huge boom," he said. "They said the world would end next year, but I thought it had come early."

*

Too Little, Too Late

At the Patong Beach Bungalows in Phuket, Thailand, Bruce Hugman, a 59-year-old British medical writer, was awakened by a thud like someone pounding on his door.

He had not felt the quake an hour and 45 minutes earlier, and now wondered drowsily if he should sleep a little longer or get to the breakfast buffet before the resort stopped serving. The water seeping under the door soon made the question moot.

Hugman's first instinct was to stack his luggage on the bed to keep it dry. But a moment later, he recalled from his hospital bed, "water was pouring in, as if it had been injected."

When Hugman pulled back the curtain, he was confronted with a wall of water that rose above the top of the window. The glass did not break, but the pressure of the wave prevented Hugman from even turning the front-door handle to get out.

"That was my first near-death moment," he said. "If the window had blown in, I surely would have drowned."

Instead, the water receded with a loud sucking sound.

Wearing just the underpants he had slept in, Hugman opened his door to an eerie scene: the sky dark, 3 feet of "syrupy brown water with all this stuff floating in it" covering the beach and no sign of any other people.

"I'm on my own," Hugman thought, wondering if he had slept through an evacuation warning.

There was none. In Bangkok, the Thai capital, government officials had seen the U.S. bulletin that a tsunami was possible near the quake's epicenter. They hesitated to issue what could have been a false alarm at the height of winter tourist season. Each year Thailand draws 12 million tourists, mostly Europeans, to its pristine beaches — a key part of the nation's economy.

"There wasn't much information. There was quite a short time," said Amorn Chantananvivate, a senior official in the meteorology department.

Instead of an evacuation order, the department put two bulletins on its website, both too little and too late. The first, an hour and 21 minutes after the quake, advised that the temblor "would be felt in parts of Thailand," according to the text printed in the Bangkok Post.

The next bulletin advised fishermen of 9- to 15-foot waves and warned of high tides on some beaches. It came about two hours after Hugman had fled his bungalow.

The retreating water gave Hugman time to join a Swedish friend at the unit behind him. As a second wave hit, the two escaped by standing on the narrow ledge of a concrete patio railing and holding on to the side of the bungalow. They watched as refrigerators and gas canisters floated past in the churn.

Once again, the water retreated. A man standing on a neighboring roof said he saw a third wave coming in.

Still on the railing, Hugman and his friend tucked their heads under the eaves of the bungalow roof in an attempt to shield themselves from the surging debris. But the water rose higher than the last time.

As Hugman gripped the roof, the tsunami lifted his legs until he was floating horizontally. Once again, the water abruptly retreated, pulling off Hugman's underwear as it went.

He fled with the others up the hill to the paved road that runs above the beach. The small shops that once lined the street had been ransacked by the waves. A bag of T-shirts bobbed past; Hugman grabbed a few to cover himself and continued to run.

*

'Pray for the People'

In Madras, about two hours after he had first felt the tremor — about an hour and a half since the mayday signal from Car Nicobar — Father Maria was back in the cathedral leading Mass when he heard a whisper from the catechist.

The man was shaking as he approached. "The seawater has reached the steps to the beach, so kindly pray for the people," he said. "And try to finish it fast, Father."

In just a few minutes, Father Maria rushed to the concrete steps behind the compound's school campus. The sea had climbed about 15 feet and stopped, as if by a miracle, just inches before it would have flooded the cathedral grounds.

The water was an oily black. But Father Maria immediately thought of the Red Sea and Charlton Heston as Moses.

"I saw the picture 'The Ten Commandments,' " he said.

"That was only cinema. We didn't believe it. But here we saw it. Naturally, it created some shock."

Outside the church, umbrella repairman Raju, 45, and his sister Maliga, 37, had been sitting in the sand in front of their shanty on the beach, chatting and watching the fishermen come and go.

The surf, about 30 yards away, had not betrayed the tsunami that was still racing beneath the surface of the ocean, gradually slowing down as it neared shore.

As the wave hit the more shallow coast, Maliga heard only the idle chatter of her family and friends against the white noise of morning life in the shanties.

"We didn't hear anything," said Maliga, who, like many Indian Tamils, uses one name. "It was like a silent wave."

Only when they saw the water suddenly rising did they know something was wrong. At the first scream from the shoreline, they ran for the steps up to the church and watched the sea swallow their one-room home.

Nine miles away, from the control tower on one of the piers at the harbor of Madras, signal boatswain Guruswamy Napolean, had a 270-degree view of one of southeastern India's busiest ports. About 9:05 a.m., just before Father Maria's catechist whispered his warning, Napolean noticed a swirling eddy of white foam, like water being pulled down a large drain. He wondered aloud whether it was a big fish. The rest of the crew laughed.

Less than five minutes later, a wall of water stretched across the horizon.

"It looked as if the whole ocean was boiling over," said Capt. Anil Kumar Prasad, 47, a harbor pilot. "The water was just rising up, spilling over the breakwater and covering the entire jetty."

The flood into Madras knocked out the control tower's power. Then, just when Napolean thought the worst was over, the water level in the harbor suddenly dropped, and the current started to suck the ships toward the sea.

The first to go, a container ship about 650 feet long and weighing up to 12,000 tons, snapped free of its bonds. The order went out over the radio for all ships to drop anchor.

The towers' radios crackled with panicked voices from ships' bridges.

"I just kept hearing people shouting at me: 'Please, I need immediate assistance! I need immediate assistance!' " Napolean recalled. " 'I need help! I need help!' "

In the enclosed harbor, hulking ships converged in a tight circle as the water swirled and the masses of steel collided like drunken sailors.

About half an hour later, the Internet and 24-hour TV news stations began to broadcast the first reports of death and mayhem around the Indian Ocean.

*

Hurried Warnings

At the tsunami center in Hawaii, McCreery and his colleagues improvised a warning system, rushing to contact officials in countries that could be the wave's next victims. They talked to U.S. consular officials across the Indian Ocean in Madagascar and Mauritius, who said they would relay warnings to Somalia and Kenya.

More data arrived. Scientists boosted their magnitude estimate again, to 9 — 10 times larger than the first estimate — confirming that the quake was one of the most powerful in a century. Only then did people and technology catch up with the wave.

In this case, the warnings proved effective. Even in Somalia, where little centralized authority exists, word of mouth carried the warnings to some fishing villages and may have saved many lives.

In Kenya, only one person died. "Officials were on TV and radio, ordering beaches closed and telling hotels to bring back their guests," said Mike Fitzpatrick, political counselor at the U.S. Embassy in Nairobi.

"They really responded," he said. "It may be a coincidence that the president of Kenya was also vacationing on the coast — that may have made them a little more attentive."

About eight hours after the disaster began, the White House summoned U.S. officials to a 4 a.m. meeting in Washington to begin planning a response.

The quake and tsunami had killed more than 80,000 people in Indonesia, 4,500 in Thailand, 28,000 in Sri Lanka, 9,000 in India and several hundred in half a dozen other nations, with the figures expected to grow. Millions were left orphaned, homeless, bereft. Families in Europe and Israel, South Korea and the United States began frantic searches for missing loved ones.

The world watched in horror as the scope of the disaster unfolded, the death toll doubling and redoubling.

Doubts haunted the scientists at the tsunami warning center in Hawaii, the ones who had caught the first glimmers of impending catastrophe from seismographs.

Should we have known the wave was coming? they asked themselves. What else could we have done? Might a phone call to the right person at the right time have saved more lives?

Amid thousands of accounts of loss and survival, one hit Weinstein particularly hard. It was of a woman in Banda Aceh looking for her 11 children swept away in the flooding.

"That was a kick in the stomach. How do you overcome something like that?" he said a few days later.

Added his colleague, Hirshorn: "It is this scar that is going to be there forever."

*

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Watson reported from Madras, Demick from Seoul and Fausset from Honolulu. Staff writers Richard C. Paddock in Banda Aceh, Bruce Wallace in Phuket, Mark Magnier in Colombo, Elizabeth Shogren and Sonni Efron in Washington and Thomas H. Maugh II and Monte Morin in Los Angeles contributed to this report.