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When two tectonic plates beneath the
Indian Ocean cracked past each other at
0:59
GMT on 26 December 2004, the sea
floor was forced upwards by some 10
metres. This displaced in the region of a
trillion tonnes of water, driving it towards
southeast Asia’s coastline in a long, low-
amplitude wave travelling at up to 900 kilo-
metres per hour.
When the wave reached shallower water
near the coast,it shortened, slowed and gath-
ered into surges that killed at least 150,000
people across a dozen countries. In the after-
math of the disaster, casualties continue to
mount at a ferocious pace.
Seismologists knew about the magnitude
9 earthquake within minutes (see ‘Triple slip
of tectonic plates caused seafloor surge’,
below), but the absence of monitoring
equipment in the ocean itself meant that
they didn’t know for sure that a tsunami had
occurred. Those who suspected as much
were unsure how to get the word out to the
regions most at risk.
Although the small global community of
tsunami researchers had expressed some
concerns about the risk of such an event,
little had been done to plan for it. “It is
news
NATURE
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VOL 433
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6 JANUARY 2005
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www.nature.com/nature 3
Past events
The history of
tsunamis offers
clear lessons
p4
Under attack
Indian government
faces outcry over
lack of warning
p5
Back to Earth
Balloon touches
down after hunt
for antimatter
p6
Blown out
Bid to grow
marijuana for
research fails
p7
Inadequate warning system left
Asia at the mercy of tsunami
Devastated: the shattered remains of Meulaboh in Indonesia, largely destroyed by the tsunami.
D. ALANGKARA/AP
In the aftermath of the tsunami that devastated
coastlines around the Indian Ocean, experts are
piecing together details of the seismic slip that
sparked the waves. The earthquake, the world’s
biggest for more than 40 years and the fourth
largest since 1900, has literally redrawn the map,
moving some islands by up to 20 metres.
The destruction, which claimed as many as
150,000 lives, was unleashed by a ‘megathrust’
— a sudden juddering movement beneath the
sea floor. A build-up of pressure caused the floor
of the Indian Ocean to lurch some 15 metres
towards Indonesia, burrowing under a tectonic
plate and triggering the ferocious swells that
smashed into surrounding shores.
The earthquake followed almost two
centuries of tension during which the India plate
pressed against the Burma microplate, which
carries the tip of Sumatra as well as the
Andaman and Nicobar Islands. The plates move
against one another at an average rate of about
6 centimetres a year, but this movement does
not occur smoothly. There has not been a very
large quake along this fault since 1833 — a fact
that may have contributed to the huge force of
this one. The India plate’s jarring slide released
the tension on the Burma microplate, causing it
to spring violently upwards.
Quakes of this type, called subduction
earthquakes, are commonplace throughout the
world, but rarely strike with such force, says
Roger Musson of the British Geological Survey
in Edinburgh. “This is the largest earthquake I’ve
seen in my career as a seismologist,” he says.
“The length of the rupture was 1,200 kilometres
— I could hardly believe it.”
The earthquake, measured at magnitude 9.0,
actually consisted of three events that occurred
within seconds of each other, Musson explains.
The initial slip, which happened to the west of
Sumatra’s northern tip, triggered two further slips
to the north. The total force released was enough
to jolt the entire planet.
The seafloor bulge unleashed a wave that
surged through the Indian Ocean. Initially, the
energy of such a wave is distributed throughout
the water column, and surface perturbation is
small. Only when the water grows shallow, near
the coast, does the wave emerge on the surface
as a tsunami — the name is Japanese for
‘harbour wave’. In this case, the wave hit
Indonesia and Thailand within an hour, and
then Sri Lanka and India, ultimately reaching
as far as eastern Africa.
Michael Hopkin
Triple slip of tectonic plates caused seafloor surge
6.1 News 3-5 NR 4/1/05 3:55 pm Page 3
Nature
Publishing
Group
© 2005
Indonesia
Malaysia
India
Thailand
Sri Lanka
3,500 km
4,000 km
4,500 km
5,000 km
5,500 km
6,000 km
1,500 km
1,000 km
500 km
Somalia
Date: 26/12/2004
Time: 00.58
GMT
Magnitude: 9.0
Date: 26/12/2004
Time: 04.21
GMT
Magnitude: 7.5
2,000 km
2,500 km
3,000 km
Andaman &
Nicobar Islands
Worst-affected areas
Affected countries
Seychelles
Seychelles
Kan du
Huludu
Male
Maldives
Maldives
Epicentre
The tsunami driven by an oceanic earthquake caused widespread destruction, as shown by these views of Banda Aceh, Indonesia, before and after the disaster.
always on the agenda,” says Vasily Titov, a
tsunami researcher at the Pacific Marine
Environmental Laboratory in Seattle, Wash-
ington.But he says that it has been difficult to
raise the money for a monitoring system.
“Only two weeks ago it would have sounded
crazy,”he says.“But it sounds very reasonable
now. The millions of dollars needed would
have saved thousands and thousands of lives.”
The most recent comparable event in the
region took place in 1883 (see ‘Tsunamis: a
long-term threat’, right). In contrast, earth-
quakes in Chile in 1960 and Alaska in 1964
led to the creation of a reasonably sophisti-
cated tsunami warning system in the Pacific
Ocean. Two international tsunami warning
bodies exist under UNESCO’s Intergovern-
mental Oceanographic Commission (IOC):
the International Coordination Group for
the Tsunami Warning System in the Pacific,
known as ITSU, and the International
Tsunami Information Center based in
Hawaii. They get by on annual budgets from
the IOC of about US$40,000 and $80,000,
respectively, which are supplemented by
grants from nations on the Pacific rim.
Displacement data
To predict a tsunami with any useful time
advantage, researchers say, data on small
changes in sea level and pressure have to be
collected directly from the floor and surface
of the ocean. The strength of the event
depends on the displacement of the ocean
floor, not on the strength of the earthquake.
Some buoys that could provide such data
are already in place in the Indian Ocean.And
only a few weeks before the tsunami struck,
members of ITSU were talking about how
these could be adapted for use in a tsunami-
warning system, says Peter Pissierssens, head
of ocean services at the IOC.
Within 20 minutes of the earthquake, at
least three monitoring stations in the United
States had detected it, initially estimating its
magnitude to be around 8.The United States
Geological Survey (USGS) circulated the
information to about 100 people, mostly its
own researchers and senior officials, within
16 minutes,and sent a more detailed bulletin
to a list of external contacts,including the US
Department of State, after an hour. The
USGS has no responsibility for tsunami
monitoring and its statement did not men-
tion the risk of such an event.
The Hawaii-based Pacific Tsunami
Warning Center (PTWC), meanwhile, sent
out a bulletin to its regular circulation list,
noting that the event presented no tsunami
risk in the Pacific. According to Laura Kong,
director of the International Tsunami Infor-
mation Center, “let’s keep an eye on it” was
the prevalent attitude that night. “At that
point, none of us expected anything like
what we have seen,” says Charles McCreery,
director of the PTWC and deputy chair of
news
4 NATURE
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Last month’s tsunami tragedy, shocking as it was,
had ample historical precedent. On 1 November
1755, for example, a fire following an earthquake
destroyed two-thirds of Lisbon, Portugal. In panic,
the population sought shelter near the shoreline,
only to be hit by waves said to be as high as
houses. More than 60,000 people died.
Devastating tsunamis are known in historical
times to have affected the populated coasts of
Papua New Guinea, Japan, Hawaii, Crete, Sicily
and the Crimea — to name just a few. In the
Pacific region, where 80% of all tsunamis occur,
a 1947 analysis indicated that seismic sea waves
higher than 7.5 metres occur on average every 15
years
1
. Records going back to 684
BC
refer to four
Pacific tsunamis higher than 30 metres.
Outside the Pacific, tsunami frequencies
have been studied in some detail only for the
Aegean and Black Sea regions. Records there
reveal that the coastal and surrounding areas
of Turkey have been affected by more than 90
tsunamis over the past 3,000 years
2
.
For most other areas, information concerning
the return periods of tsunamis is scarce. A rough
comparison of tsunami frequencies in different
parts of the globe was done in 2000 by the
London-based Benfield Hazard Research Centre,
as part of its Tsunami Risks Project. The resulting
risk analysis estimates the return periods of
10-metre waves to be about 1,000 years for
the North Atlantic and Indian oceans, southern
Japan and the Caribbean, 500 years for the
Philippines and the Mediterranean Sea, 250
years for Alaska, South America and Kamchatka
in eastern Siberia, and less than 200 years for
Hawaii and the southwest Pacific.
The south Asian disaster will have a “huge
effect” on instigating more thorough risk
assessments, predicts Bill McGuire, a
volcanologist and director of the London
research centre, as well as encouraging
preventive measures in threatened
regions.
Quirin Schiermeier
➧ www.nerc-bas.ac.uk/tsunami-risks
1. Heck,N.H.Bull. Seismol. Soc. Am. 37, 269–286 (1947).
2. Altinok, Y. & Ersoy, S. Nat. Hazards 21, 185–205 (2000).
Tsunamis: a long-term threat
RELIEFWEB
DIGITALGLOBE
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Nature
Publishing
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© 2005
ITSU.“We expected a local tsunami at most.”
At 2:04
GMT, the PTWC put out another
bulletin revising the quake up to magnitude
8.5. Because there was no information about
sea levels in the area, the existence of a
tsunami was merely hypothetical, but staff
were worried enough to begin looking for
numbers to call in Asia.
Communication breakdown
According to Kong, the team tried and failed
to reach colleagues in Indonesia. Australia
was contacted, although to little avail, as that
country experienced only half-metre waves.
It was not until 3:30 that the team in Hawaii
saw news reports on the Internet of casual-
ties in Sri Lanka. The wave had already
crossed the ocean, to devastating effect.
Kong says that without a predetermined
communication plan, warning efforts were
doomed from the start. But she adds that the
PTWC will in future directly contact the US
state department, which can communicate
risks to any nation,at any time.
Indonesian seismologists initially under-
estimated the strength of the earthquake,
according to local news reports. And
although officials there had very little time in
which to act, an instrument that could have
helped warn them of the approaching
wave was transmitting its information to a
dead phone line, according to a senior Indo-
nesian seismologist (see news@nature.com
doi:10.1038/news041229-4 ; 2004).
Efforts over the years to get an Indian
Ocean warning system in place have made
little progress in the face of national govern-
ments’ reluctance to invest in them. In 2003,
a working group on the Tsunami Warning
System in the Southwest Pacific and Indian
Ocean was established within ITSU. But
Pissierssens says that the first chair of the
group, a representative from Indonesia, left
soon after his appointment and that the
group then split into two according to region.
Phil Cummins a seismologist at Geo-
science Australia in Canberra agreed to write a
position paper for the group on tsunami risk
in the Indian Ocean.“I am still in the process
of writing that paper,” he says. “No one else
was 100% convinced that we should worry
and that included me,I’ve got to admit.”
According to Pissierssens, UNESCO will
now make an observation system in the
Indian Ocean a priority. “The first thing we
will do is send out a survey team in January or
February,”he says,“and then we want to set up
news
India’s government and scientific establishment
have been heavily criticized for failing to provide
warning of a tsunami that drowned at least
12,000 people on the nation’s eastern coast.
Newspapers and opposition spokesmen
have asked why a country with India’s scientific
resources couldn’t better prepare for such an
event. Ministers immediately pledged up to
US$29 million to build a tsunami-monitoring
system, and promised to seek more cooperation
with the Pacific Tsunami Warning Center in Hawaii.
“This is not a knee-jerk reaction. We are very
serious,” science and technology secretary
Valangiman Ramamurthi told Nature. “We are
going to have a brain-storming meeting this
month to decide how we should proceed and we
have invited experts from the United States,” he
said. In response to criticism, he added: “We
cannot join a Pacific network as India is not in
that region. And you do not make heavy
investment to warn against something that
happens once in a century.”
The ocean development secretary, Harsh
Gupta, told a press conference in New Delhi
that there was no record of a tsunami ever hitting
the Indian coastline, even as other government
ministers acknowledged such events in 1833
and 1883.
“No government thought of it,” says science
minister Kapil Sibal. “The last recorded tsunami
was in 1883. It was not in the horizon of our
thoughts.” India now plans to install a network of
10 to 12 seafloor pressure sensors to be imported
from the United States, as well as several floating
sensors on ocean buoys, linked to an Indian
geostationary satellite.
Critics say that the tragedy exposed a major
weakness in the current system, which
authorizes only the Indian Meteorological
Department to put out hazard alerts. “Data were
pouring into our lab but we cannot issue alerts
even if we can analyse the data for tsunami
potential,” says one researcher at the National
Geophysical Research Institute in Hyderabad.
They also want to know why the Indian air
force, whose base in Car Nicobar Island was
submerged by tides an hour before the waves hit
the mainland, failed to provide any public warning.
The tsunami spared India’s main rocket
launch site at Sriharikota Island, 80 kilometres
north of Chennai. But it damaged cooling
water pumps at a nuclear power station at
Kalpakkam, leaving staff with very little time
to shut down the plant safely. “The tsunami
factor was not taken into account,” says Anil
Kakodkar, chairman of the Atomic Energy
Commission. “From now on, it will be
factored in.”
K. S. Jayaraman, New Delhi
India pledges to fund alert system in wake of disaster
a conference in the area.”Needless to say, there
is little reluctance now to accept the need for
the system.The UN International Strategy for
Disaster Reduction has also said that one
should be built within a year. And the Indian
government, under intense domestic pressure
for its failure to warn people on its eastern
coast, said it would spend up to US$29 million
to build a system itself (see ‘India pledges to
fund alert system in wake of disaster’,above).
Nicole Rencoret, spokeswoman for the
UN’s disaster-reduction branch, notes that
early warning systems could watch for other
natural disaster risks, as well as tsunamis.
“There has been an enormous amount of
focus on tsunamis, but we need to take a
multihazard approach,”she says.
■
G. OSAN/AP
DIGITALGLOBE
Tu r ning tide: the waters of the Indian Ocean tsunami recede after battering the coast of Sri Lanka.
NATURE
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Relief centres in India have been inundated with
people in need of food and aid.
6.1 News 3-5 NR 4/1/05 3:55 pm Page 5
Nature
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© 2005
