By Thomas K. Grose
On the morning of Dec. 26, 2004,
a massive earthquake along the Sumatra
Fault, lying off the coast of Indonesia,
triggered a huge tsunami, the likes
of which the world had not seen
in 45 years. Huge waves spawned
by the quake devastated coastal
communities in 11 south Asian countries.
As of this writing, the death toll
stood at 154,000, but the final
tally will likely near 300,000.
Yet, experts say, the fatalities
caused by the Asian tsunami could
have been far fewer, even without
the sophisticated warning systems
found along tsunami-prone coastal
areas of the United States. They
blame a lack of public education,
shoddy building design and construction,
and poor zoning for the huge loss
of life. To help ensure that future
tsunamis are less lethal, at least
two teams of researchers led by
American engineering professors
headed to the tsunami-ravaged region
in early January to survey the damage.
Unlike hurricanes and earthquakes,
tsunamis are relatively rare natural
disasters, a fact that makes predicting
their behavior difficult. Hydrologists
and hydrodynamicists use numerical
models to forecast how tsunamis
will interact with land and buildings,
and that information can be used
for warning systems, for public
education, and to improve building
and zoning in tsunami-threatened
areas. And evidence amassed in the
wake of a tsunami helps researchers
to fine-tune and improve those models.
"Going out into the field
and getting data is one of the most
important things you can do in tsunami
science because the events are so
very rare," explains Patrick
Lynett, an assistant professor at
Texas A&M University's
Ocean Engineering Program. Lynett
was part of a team of eight researchers—engineers,
geologists, and hydrogeologists
from American universities as well
as the U.S. Geological Survey—who
spent a week in Sri Lanka, mostly
on its east and south coasts. That
team was led by Philip Liu, a professor
of civil and environmental engineering
at Cornell University. Harry Yeh,
a professor of ocean engineering
at Oregon State University, led
a second team to the east coast
of southern India, where it spent
five days in the field, covering
about 215 miles. His six-member
team included two Indian researchers—a
seismologist and an ocean scientist—as
well as a social engineer from Japan.
Researchers face severe time constraints
while trying to get into disaster
zones. They must wait until critical
rescue missions and body collections
are mostly complete, but if they
wait too long, key evidence might
disappear as cleanups commence.
"This trip was timed well—there
was plenty of evidence," says
Liu, whose team arrived in Sri Lanka
in early January.
The two key things the engineers
were trying to learn were the maximum
water levels onshore and the inundation
zone, or how far inland the water
came. They looked for waterlines
and mud marks on buildings and tree
damage. How high the water reached
tree trunks is very clear, Liu says.
"The tree bark is torn apart."
Debris hanging in tree branches
can also indicate water levels,
while debris lines denote how far
the water came ashore. The accumulated
evidence, Lynett says, "can
give you a whole profile of the
of the areas in Sri Lanka are relatively
flat, and water levels there ranged
from around 10 to 20 feet. But where
elevations were steeper, the water
raged even higher, up to around
38 feet in parts. "It [the
water] just shoots right up the
slope," Lynett says. The amount
of inundation also varied. In some
locales it petered out after about
160 feet; in other areas, it flowed
inland about a mile and a quarter.
Water levels measured by Yeh in
India ranged from around 9 feet
to 16 feet at Nagapattinum, where
6,000 people perished.
From the Past
Those data are compared with existing
models. The researchers are finding
that in some cases their models
were quite accurate, while other
times they overestimated levels
in some areas and underestimated
in others. The data can also be
calculated back to their source
to help scientists get a better
idea of what the seafloor looks
like where underwater quakes occur.
While scientists can quickly measure
how much energy is released from
a quake, the question of how the
ocean floor was displaced, how the
fault ruptured, for example, remains
The Sri Lanka team found that some
surviving buildings that faced the
ocean nevertheless had their back
walls blown out. As the water filled
those buildings, the growing pressure
forced the back walls to burst.
teams also found deep scarring on
the foundations of some buildings.
They determined that as the water
was funneled between rows of houses
and buildings it accelerated. As
the charging water hit the corners
of buildings, whirlpools formed
that scarred and undermined the
foundations of buildings erected
on sand. Yeh called this finding
"very significant" for
the future design of tsunami-proof
Because the tsunami struck during
daytime and inundated many populated
areas, the researchers were also
able to gather eyewitness accounts.
Indeed, Yeh says, there is also
plenty of videotape footage and
photographic evidence that is proving
useful. Liu says that his interviews
with locals lead him to conclude
there were three waves that day,
with the second being the strongest.
Another boon for the researchers
is remote-sensor images taken from
government and commercial satellites,
a first in post-tsunami investigations.
Yeh calls the images amazing and
very helpful. "In just two
to three years the technology advancement
has been incredible." In damage
surveys, Yeh explains, "there
are a lot of false clues"
on the ground, and the satellite
images can help investigators avoid
them. For instance, Yeh came across
several fishing boats piled together.
He wasn't sure if the wave
or the cleanup crews pushed them
there. When he checked the satellite
images taken not long after the
tsunami receded, the boats were
not there. He concluded the cluster
As a tsunami races across open
seas it can reach speeds of nearly
600 mph, as fast as a commercial
airliner. But it slows greatly once
it strikes land. The wave drops
sediment as it slows, and geologists
measure sediment deposits to factor
the wave's land speed. That
work is still being done, but Lynett
says a ballpark estimate is between
20 to 30 mph.
Researchers say ongoing, frequent
public education efforts are the
best way to avoid huge fatalities
from tsunamis. "It is not
too difficult to avoid loss of life,"
Liu insists. "And the cheapest
way to mitigate a tsunami is with
education," letting people
know when a tsunami is likely (such
as after a deep sea earthquake)
and what the warning signs are.
The people who died in Sri Lanka
had only to head inland anywhere
from a few dozen yards to, at most,
a mile and a half to reach safety.
And they could have done that had
they known the danger signals, such
as a receding sea.
Tsunamis occur relatively frequently
in parts of Japan. As a result,
people living in coastal areas know
when to evacuate. When a 30-foot-high
wave took out an entire Japanese
village a decade ago, only three
people died. In Sri Lanka, between
the smaller first wave and the much
larger second wave, the water receded
far out into the seabed. Instead
of using that opportunity to head
for safe ground, some people wandered
out to look at the seashells and
Education programs, however, can
be weakened by the potentially long
lag periods between tsunamis. After
a few years, memories of the horrors
and the need to heed warning signs
can ebb like the tide. Yeh says
a silver lining from this disaster
is "now everybody is aware
of the tsunami threat—at least
for the next two or three years."
Zoning is a key safety measure,
too. Liu's team visited the
remains of a hospital that was built
about 50 yards from the shoreline.
All the facility's doctors,
nurses, staff and patients—300
people in all—were killed.
And, of course, the loss of so much
medical personnel undermined the
town's post-wave rescue efforts.
Liu says "I still get very
emotional about that, just thinking
about it." But the tragedy
underscored how important it is
not to build critical infrastructure—hospitals,
schools, and police and fire stations—in
Tsunami-resistant buildings can
be designed and built, the engineers
say, some perhaps with open designs
on the lower floors that will let
rushing waters flow through. Yeh
envisions tsunami shelters, either
single-purpose ones, or multipurpose
buildings designated as shelters.
Building code enforcement is a must,
too. Liu saw many supposedly sturdy
brick buildings demolished because
they weren't reinforced.
researchers confess to being awestruck
by the destructive power nature
can unleash. Liu has been on many
surveys, including one after a large
tsunami battered Indonesia in 1992.
But that wave hit an area that was
sparsely populated. So the difference
between that inspection and Sri
Lanka's was stark, he says.
"What shocked me was the magnitude
of the devastation." This
was Lynett's first survey,
and he says words don't do
justice in describing the destruction
he saw. "It really was like
Thomas K. Grose is a freelance
writer based in Great Britain.