• The 9.0 Earthquake at 6.58 hours at the epicenter (and in Sri Lanka) led to a sequence of 15 other quakes across the Andaman region.
  
• While earthquakes could not be predicted in advance, once the earthquake was detected it would have been possible to give about 3 hours of notice of a potential Tsunami. Such a system of warnings is in place across the Pacific Ocean. However, there was no warning system in the Indian Ocean. In addition, coastal dwellers are educated in the Pacific littoral to get to high ground quickly following waves. However, those in the Indian Ocean were quite unaware.
  
• Tsunamis are rarer in the Indian Ocean as the seismic activity is much less than in the Pacific. However, there have been 7 records of Tsunamis set off by Earthquakes near Indonesia, Pakistan and one at Bay of Bengal.
  
• Earthquakes occur when any of the 12 or 13 plate collide at their boundaries. The present collision is due to compression between the Indian and Burmese plates. Scientists now believe that one plate that comprised the landmass from India to Australia has broken up into two. The initial 8.9 eruption happened near the location of the meeting point of the Australian, Indian and Burmese plates. Scientists have shown that this is a region of compression as the Australian plate  is rotating counterclockwise into the Indian plate. This also means that a region of seismic activity has become active in the South Eastern Indian Ocean.
  
• Tsunamis are not entirely unknown in Sri Lanka. For example, the Tsunami in 1883 generated by the Volcanoes at Krakatoa led to a surge of at least 1 m in Sri Lanka. The damage was much less then. However, one difference was that this particular episode happened in the month of August. In the month of December, under the North-East monsoon, the Equatorial Indian Ocean jet propagates along the equator from Sumatra (near the epicenter of the quake) slightly to the South of Sri Lanka and to Somalia. This may be why the impact of the quake led to severe impacts in Sri Lanka.
  
• Once the large amount of pent-up energy in the compression zones of the plate boundaries have been released, it takes another buildup of energy for another event of similar magnitude. This is unlikely in the short-term. However, in the future, Indian Ocean littoral regions should generate and pay attention to earthquake and tsunami warnings and be aware of the interplay of the seasonal oceanographic currents.
  

................. TSUNAMI INFORMATION BULLETIN ..................

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 W COAST OF NORTHERN SUMATERA
 MAGNITUDE   -  9.0

EVALUATION

 SOME ENERGY FROM YESTERDAYS TSUNAMI IN THE INDIAN OCEAN HAS
 LEAKED INTO THE PACIFIC BASIN... PROBABLY FROM SOUTH OF THE
 AUSTRALIAN CONTINENT.  THIS ENERGY HAS PRODUCED MINOR
 SEA LEVEL FLUCTUATIONS AT MANY PLACES IN THE PACIFIC.  FOR
 EXAMPLE...

  50 CM CREST-TO-TROUGH AT CALLAO CHILE
  19 CM CREST-TO-TROUGH AT IQUIQUE CHILE
  13 CM CREST-TO-TROUGH AT PAGO PAGO AMERICAN SAMOA
  11 CM CREST-TO-TROUGH AT SUVA FIJI
  50 CM CREST-TO-TROUGH AT WAITANGI CHATHAM IS NEW ZEALAND
  65 CM CREST-TO-TROUGH AT JACKSON BAY NEW ZEALAND
  18 CM CREST-TO-TROUGH AT PORT VILA VANUATU
  06 CM CREST-TO-TROUGH AT HILO HAWAII USA
  22 CM CREST-TO-TROUGH AT SAN DIEGO CALIFORNIA USA

 HOWEVER... AT MANZANILLO MEXICO SEA LEVEL FLUCTUATIONS WERE
 AS MUCH AS 2.6 METERS CREST-TO-TROUGH PROBABLY DUE TO FOCUSING
 OF ENERGY BY THE EAST PACIFIC RISE AS WELL AS LOCAL RESONANCES.

 THIS IS TO ADVISE THAT SMALL SEA LEVEL CHANGES COULD CONTINUE
 TO BE OBSERVED ACROSS THE PACIFIC OVER THE NEXT DAY OR TWO
 UNTIL ALL ENERGY FROM THIS EVENT IS EVENTUALLY DISSIPATED.

THIS WILL BE THE FINAL BULLETIN ISSUED FOR THIS EVENT UNLESS
ADDITIONAL INFORMATION BECOMES AVAILABLE.

THE WEST COAST/ALASKA TSUNAMI WARNING CENTER WILL ISSUE BULLETINS
FOR ALASKA - BRITISH COLUMBIA - WASHINGTON - OREGON - CALIFORNIA.


**************************************************************


TSUNAMI BULLETIN NUMBER 002
PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED AT 0204Z 26 DEC 2004

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

.................. TSUNAMI INFORMATION BULLETIN ..................

ATTENTION: NOTE REVISED MAGNITUDE.

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 W COAST OF NORTHERN SUMATERA
 MAGNITUDE   -  8.5

EVALUATION
 REVISED MAGNITUDE BASED ON ANALYSIS OF MANTLE WAVES.
 THIS EARTHQUAKE IS LOCATED OUTSIDE THE PACIFIC. 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.                                                         

THIS WILL BE THE ONLY BULLETIN ISSUED FOR THIS EVENT UNLESS
ADDITIONAL INFORMATION BECOMES AVAILABLE.

THE WEST COAST/ALASKA TSUNAMI WARNING CENTER WILL ISSUE BULLETINS
FOR ALASKA - BRITISH COLUMBIA - WASHINGTON - OREGON - CALIFORNIA.




**************************************************************

The tectonics of the region is complex and involves the interaction of the Australian, Sunda and Eurasian plates in addition to the India and Burma plate. The India and Australia plates move northeastwards at a rate of about 6 cm/year relative to the Burma plate. This results in oblique convergence at the Sunda trench. Some of this oblique motion is accommodated on the right-lateral transform faults and rifts that separate the Burma and Sunda plates.

Preliminary locations of larger aftershocks following the megathrust earthquake show that approximately 1000 km of the plate boundary slipped as a result of the earthquake. Aftershocks are distributed along much of the shallow plate interface and primarily extend northwards of the epicenter to the Andaman Islands.

The worlds largest recorded earthquakes were all megathrust events and occur where one tectonic plate subducts beneath another. These include: the magnitude 9.5 1960 Chile earthquake, the magnitude 9.2 1964 Prince William Sound, Alaska earthquake, the magnitude 9.1 1957 Andreanof, Alaska earthquake, and the magnitude 9.0 1952 Kamchatka earthquake. As with the recent event, megathrust earthquakes often generate large tsunamis that can cause damage over a much wider area than is directly effected by ground shaking near the earthquake's rupture.

Scientists at Columbia University's Lamont-Doherty Earth Observatory report direct evidence that one of the Earth's great crustal plates is cracking in two - 1995.

In a report published in the most recent issue of Earth and Planetary Science Letters (vol. 133), the scientists say they have confirmed that the Indo-Australian Plate--long identified as a single plate on which both India and Australia lie--appears to have broken apart just south of the Equator beneath the Indian Ocean. The break has been underway for the past several million years, and now the two continents are moving independently of one another in slightly different directions.

Scientists have known that for some 50 million years, the Indian subcontinent has been pushing northward into Eurasia, forcefully raising the Tibetan Plateau and the Himalayan Mountains. The new research suggests that starting about 8 million years ago, the accumulated mass became so great that the Indo-Australian Plate buckled and broke under the stress.

"In the Central Indian Ocean, Nature is conducting a large-scale laboratory experiment for us, showing us what happens to the oceanic lithosphere (Earth's outer layer) when force is applied," Dr. Weissel said in an interview. Essentially pushed into an immovable object, "it can buckle like a piece of tin," he said.

More recently, researchers at Northwestern University, led by Richard Gordon and Seth Stein, used data on how newly created seafloor had spread outward from mid-ocean ridges to the west and south of the deformed region in the Indian Ocean. They theorized that the movements of the newly created seafloor could be accommodated only if a distinct plate boundary existed between separate Indian and Australian plates across the equatorial Indian Ocean.

TSUNAMIS ON THE COAST LINES OF INDIA

Although the majority of the reported tsunamis are from littoral countries of the Pacific Ocean, there are a few cases of tsunamis in the Indian Ocean. The approximate length of the Indian coast is about 6000 kilometers. The coasts run from north to south and have two arms in the east and west with a tapering end at Kanyakumari. The tsunamigenic earthquakes occur mostly at the following three locations; (1) The Andaman sea, (2) Area about 400-500 kilometers SSW of Sri Lanka (Ceylon), (3) The Arabian Sea about 70-100 kilometers south of Pakistan Coast -- off Karachi and Baluchistan. The oldest record of tsunami is available from November 326 BC earthquake near the Indus delta/Kutch region. Alexander the Great was returning to Greece after his conquest and wanted to go back by a sea route. But an earthquake of large magnitude destroyed the mighty Macedonian fleet as reported by Lietzin (1974).

The earliest record of tsunami is reported to be about 1.5 meters at Chennai (formerly Madras) which was created due to the August 8, 1883 Krakatoa volcanic explosion in Indonesia. An earthquake of magnitude 8.25 occurred about 70 kilometers south of Karachi (Pakistan) at 24.5 N and 63.0 E on November 27, 1945. This created a large tsunami of about 11.0 to 11.5 meters high on the coasts of India in the Kutchch region, as reported by Pendse (1945). An earthquake of magnitude 8.1 occurred in the Andaman Sea at 12.9 N and 92.5 E on June 26, 1941 and a tsunami hit the east coast of India. As per non-scientific/journalistic sources, the height of the tsunami was of the order of 0.75 to 1.25 meters. At the time no tide gauge was in operation. Mathematical calculations suggest that the height could be of the order of 1.0 meter. There are a few more cases of earthquakes of magnitude less than 8.0 which have given rise to some smaller tsunamis. Bapat, et al (1983) have reported a few more earthquakes on the coast of Myanmar (formerly Burma).

Oceanography in the Equatorial Indian Ocean

The seas aroung Sri Lanka serves as a choke point as the ocean is in effect bounded on the South by the monsoon induced equatorial jet. Around Sri Lanka, currents that come travel along the equator, those that come from open seas and those that are driven along the coasts of India, merge, clash and set off eddies and waves. The ocean current is driven from the Bay of Bengal to the Arabian Sea during the North-East monsoon and from the Arabian sea to the Bay of Bengal during the South-West monsoon. During the NE monsoon, the East Indian Coastal Current (EICC) travels down the East coast impelled by the monsoon winds and fed by the discharge of the Ganga and other rivers along the West Coast. These currents are particularly rapid when there is heavy rains or cyclones. During the South-West monsoon, the West Indian Coastal Current (WICC) travels down the West Coast. To the South of Sri Lanka, the Equatorial Monsoon Current (EMC) flows West and East during the South-West and North-East monsoons respectively.

The equatorial jet travels at around 1 m/s (Tomzack and Godrey, p 201-203) or around 3-4 km / hour. Indeed, this is much slower than the speed of the Tsunami of 500 km/hour. Perhaps, the currents themselves may not have a serious effect on Tsunami. However, the basin topography (see below), in the way it focusses  the energy of the tsunami may indeed have effected. In particular the 94 degree N-S ridge seems to have served as "reflector" of the Tsunami wave.

Figure caption: The ocean currents during the North-East and  South-West monsoons.

F. I. González¹, H.B. Milburn¹, E.N. Bernard¹, J. Newman²

¹Pacific Marine Environmental Laboratory / NOAA
Seattle, WA 98115

²Joint Institute for the Study of the Atmosphere and Ocean / U. Washington
Seattle, WA 98195

New York Times

December 27, 2004

With No Plan for a Warning, Indian Ocean Was Exposed

he earthquake that struck northwest of Sumatra, Indonesia, at dawn yesterday was a perfect wave-making machine, and the lack of a tsunami warning system in the Indian Ocean essentially guaranteed the devastation that swept coastal communities around southern Asia, experts said.

Although waves swamped parts of the Sumatran coast and nearby islands within minutes, there would have been time to alert more distant communities if the Indian Ocean had a warning network like that in the Pacific, said Dr. Tad Murty, an expert on the region's tsunamis who is affiliated with the University of Manitoba in Winnipeg.

Within 15 minutes of the earthquake, in fact, scientists running the existing tsunami warning system for the Pacific, where such waves are far more common, sent an alert from their Honolulu hub to 26 participating countries, including Thailand and Indonesia, that destructive waves might be generated by the Sumatra tremors.

But there was no way to convey that information speedily to countries or communities an ocean away, said Dr. Laura S. L. Kong, a Commerce Department seismologist and director of the International Tsunami Information Center, an office run under the auspices of the United Nations.

Phone calls were hurriedly made to countries in the Indian Ocean danger zone, she said, but not with the speed that comes from pre-established emergency planning.

"Outside the Pacific these things don't occur very often at all so the challenge is how to make people and government officials aware," she said.

Tsunamis, sometimes referred to as tidal waves but having nothing to do with tidal forces, are generated when an earthquake, eruption or landslide abruptly moves the seabed, jolting the waters above.

Resulting waves can cross thousands of miles of deep ocean at near jetliner speeds as near-invisible disturbances before welling up in shallower coastal waters to heights of 30 feet or more.

But even at such speeds, prompt warnings can provide ample time to evacuate people, Dr. Murty and other experts said. The Pacific network of stations gauging wave and earthquake activity is able to alert potential targets within minutes.

Tsunamis have swept the Indian Ocean, as well, oceanographers said yesterday, noting one that killed several hundred people near Bombay in 1945 and another - one of the earliest tsunamis recorded in the region - that ravaged what is now Bangladesh and other parts of the Bay of Bengal in 1762.

With population densities enormously high in many parts of coastal southern Asia, the region should have started setting up such a network long ago, said Dr. Murty, who is originally from India.

Other scientists have voiced similar concerns. At a meeting in June of the Intergovernmental Oceanographic Commission, a United Nations body, experts concluded that the "Indian Ocean has a significant threat from both local and distant tsunamis" and should have a warning network.

But Dr. Murty said that India, Thailand, Malaysia and other countries in the region had "never shown the initiative to do anything."

"They see this as a Pacific problem," he said. "I have a feeling that after this tragedy that may change."

The earthquake near Sumatra was the fifth most potent in the world in the last 100 years and the worst in 40 years, registering a magnitude of 9.0. It was followed by more than a dozen aftershocks, but none of those was expected to produce dangerous waves, said federal geologists.

The quake occurred at one of the many seams in the ever-shifting crust of the Earth where one plate slips beneath another in an incessant, but spasmodic process. In this case, the quake was set off by an abrupt slippage along 700 miles of the seam where the plate beneath the Indian ocean slides under the Indonesian archipelago.

This caused a vast stretch of seabed to shift about 50 feet, said geologists at the National Earthquake Information Center in Golden, Colo.

The biggest danger from earthquakes on land tends to come when the earth heaves horizontally, as is the case along the San Andreas fault in California. But faults where earthquakes tend to cause abrupt vertical motion, like the ones along western Indonesia, pose the biggest risk of generating tsunamis because they can act like a giant piston, deforming the sea. In such submarine earthquakes, gravity and the incompressibility of water force the seas above to react immediately to the change thousands of feet below.

"You're taking hundreds of miles of ocean bottom and moving it dozens of feet," said David Wald, a seismologist at the center. "That displaces a huge amount of water. The water at the surface starts to shift downhill and that makes a tsunami."

Most research on such waves and efforts to create warning systems have focused on the Pacific, where the Ring of Fire, a great arcing seam of volcanic and tectonic activity, causes a significant tsunami about once a decade.

One of the first efforts to alert communities to impending tsunamis came in Hawaii in the 1920's, said Dr. George D. Curtis, a tsunami expert affiliated with the University of Hawaii at Hilo.

A geologist at Hawaii's volcano observatory, upon detecting telltale tremors, would call local harbor officials and tell them to have boats moved to safety, Dr. Curtis said. Efforts greatly intensified in 1946, after a powerful earthquake in the Aleutian island chain of Alaska unexpectedly sent waves smashing into Hawaii, killing more than 150 people.

In 1948, the United States created its Pacific Tsunami Warning Center, which has been linked to an international data and warning network since 1965.

Any underwater earthquake with a magnitude greater than 6.5 starts the process, Dr. Murty said, and if a single wave gauge signals that the ocean is reacting, an alert is issued. The system has helped prevent loss of life, but only in places where alerts can quickly be communicated.

The last catastrophic tsunami occurred in July 1998, when more than 2,500 villagers on the coast of Papua New Guinea died after a magnitude 7.0 earthquake caused an undersea landslide.

But there has been little work done outside the Pacific, other than informal discussions, to expand the tsunami monitoring network.

"There's no reason for a single individual to get killed in a tsunami," Dr. Murty said. "The waves are totally predictable. We have travel-time charts covering all of the Indian Ocean. From where this earthquake happened to hit, the travel time for waves to hit the tip of India was four hours. That's enough time for a warning."

Other experts agreed that the Indian Ocean region could reduce its vulnerability with a warning system, but said no one should expect a quick fix.

New York Times

December 28, 2004

At Warning Center, Alert for the Quake, None for a Tsunami

ONOLULU, Dec. 27 - When experts at the Pacific Tsunami Warning Center in Honolulu were first alerted that an earthquake had struck Sunday off Indonesia, they had no way of knowing that it had generated a devastating tsunami and no way to warn the people most likely to suffer.

Tsunamis are rare in the Indian Ocean, which has no system for detecting them and alerting those in danger, and scientists do not have the tools to tell when an earthquake has created one.

Not until the deadly wave hit Sri Lanka and the scientists in Honolulu saw news reports of the damage there did they recognize what was happening.

"Then we knew there was something moving across the Indian Ocean," said Dr. Charles McCreery, the center's director.

"We wanted to try to do something, but without a plan in place then, it was not an effective way to issue a warning, or to have it acted upon," Dr. McCreery said. "There would have still been some time - not a lot of time, but some time - if there was something that could be done in Madagascar, or on the coast of Africa."

"One of the things that was running through my mind is just that our international group has in many past meetings had discussions about what can be done for other ocean basins," he said. "And I guess I was just wishing in retrospect that more progress had been made in that area."

The sequence of events as knowledge of the earthquake, the tsunami and the destruction unfolded suggest the speed and precision of science and modern communication, as well as their limits. If there had been a warning system for tsunamis in the Indian Ocean, thousands of people might have had a chance to flee.

The first notice of the earthquake that anyone at the Pacific tsunami center received was a computer-generated page set off by seismic sensors at 2:59 p.m. on Saturday Honolulu time. The immediate message received by people like Laura S. L. Kong, a Department of Commerce expert who is the head of a United Nations tsunami education center in Hawaii, included the time of the quake, latitude, longitude and an initial estimate of magnitude, about 8.0.

Nobody was in the office of the Pacific tsunami center. But staff members who received the pages reached the office, took a closer look at available data and sent out a warning to a preset list of contacts around the Pacific.

The center was advising of sea level changes in Fiji, Chile and California measured in inches, the echo of a distant event that had sloshed through the straits that connect the oceans. The warning center continued to refine its estimate of the quake, eventually raising it to a magnitude of 9.0, which is 10 times more powerful than the initial estimate of 8.0, because the scale is logarithmic.

The Pacific center, operated by the National Oceanographic and Atmospheric Administration, faced two problems in recognizing what was occurring in the Indian Ocean and alerting potential victims. There is no direct connection between an earthquake magnitude and a resulting tsunami. Not all quakes under the ocean lift the ocean floor to displace the water needed to create a tsunami.

For the Pacific, there are computer models to analyze the consequences of an earthquake, based on years of observations of previous quakes and tsunamis. For the Indian Ocean, there are no such models, according to Vasily V. Titov, a research oceanographer with the Oceanographic and Atmospheric Administration, based in Seattle. "They assemble quite a bit of data to get the right information and the right warning message," he said of such models.

Another difficulty is that countries that have experienced tsunamis in recent memory are set up with warning systems. Hawaii, for example, has warning sirens, and the "weather radio" network of oceanographic administration can also carry tsunami warnings.

Nor is a tsunami obvious as it races across an ocean at hundreds of miles per hour. In the open ocean, the wave may be only inches high. Boats on the ocean would feel almost nothing. Only when it hits the shallow water of a continental shelf does the wave rise to its destructive height.

Dr. McCreery, the Honolulu center's director, said the initial estimate of the earthquake's magnitude, 8.0, would have been likely to generate a local tsunami.

"Based on it being an 8.0, we assumed the damage would be confined to Sumatra and would be a local tsunami event, one that strikes shore within minutes of the event," he said. "We weren't overly concerned at that point that it was something larger."

But using another, sometimes more accurate method of measuring, Dr. McCreery said, the staff quickly determined that the magnitude had been closer to 8.5, more intense, but still only borderline for generating more distant damage. The center issued a follow-up bulletin.

But it was not until they saw news reports of casualties in Sri Lanka that all that changed.

Dr. McCreery spoke to the American ambassador to Sri Lanka, who wanted to know whether there were more giant waves expected. Then he had a conference call with a State Department official and embassy staff in Madagascar and Mauritius to address potential threats headed their way, and how the local authorities might be notified. But with no system in place, they would basically be scrambling.

The Indian Ocean and some other ocean basins do not have tsunami warning systems. The Pacific basin has had a well-constructed warning system with instrumentation throughout the region and plans for communicating critical information since 1965, Dr. McCreery said.

He said there have been frequent international discussions about improving systems for other oceans. "I know for certain after this event the entire global tsunami community will be looking for ways to implement better preparedness," he said.

One of the few places in the Indian Ocean that got the message of the quake was Diego Garcia, a speck of an island with a United States Navy base, because the Pacific warning center's contact list includes the Navy. Finding the appropriate people in Sri Lanka or India was harder.

The experts knew they were set up for the wrong ocean, but over a holiday weekend, Dr. Kong said, "it's tough to find contact information."

"I think they made their best efforts to contact as many people they thought they could get to," she said. After pushing the button to send out the initial warning to contacts in the Pacific, where about 90 percent of the tsunamis are observed, "they're trying to think of personally who might they call, who might then know who to call."

Last year a book on another Indonesian cataclysm, "Krakatoa: The Day the World Exploded," by Simon Winchester, asserted that that volcano, which set off an even more deadly tsunami when it exploded in 1883, was the world's first international disaster, because new undersea telegraph cables spread the news around the world within a few minutes. With high-speed data links and the Internet, it takes fewer minutes now, but if the information spreads wide, it does not always go deep.

Michele Kayal reported from Honolulu for this article, and Matthew L. Wald from Washington.

Surviving a Tsunami—Lessons from Chile, Hawaii, and Japan

This 18-page booklet was originally published in paper by the U.S. Geological Survey and is now available here as a PDF document. It contains lessons on how to survive a tsunami based on accounts from people who survived the tsunami generated by the largest earthquake ever measured—the magnitude 9.5 earthquake in Chile on May 22, 1960. It also contains an excellent description of what tsunamis are.

This project was sponsored by The National Tsunami Hazard Mitigation Program. The booklet was prepared in cooperation with Universidad Austral de Chile, the University of Tokyo, the University of Washington, the Geological Survey of Japan, and the Pacific Tsunami Museum.

Download a PDF version of this report (15.7 MB)