Why the Tsunami in Palu (Indonesia) Struck Without Warning
Even as authorities struggled to
respond to the aftermath of the tsunami in Palu, they endured withering criticism
for failing to adequately prepare the area for such disasters beforehand.
Photograph by Carl Court / Getty
Fourteen years ago,
Indonesia suffered one of the deadliest disasters in modern history, a
9.1-magnitude earthquake that unleashed a sixty-foot wall of water that killed
approximately a hundred and seventy thousand people, many of them in the
northern province of Aceh. In the years following, the government invested in
preparing for the next catastrophe. In 2008, a disaster-management board was created,
which, with the help of foreign governments, including Germany and the United
States, built an early-warning system for tsunamis, made up of twenty-two
sensor-laden buoys, which cost half a million dollars each and went online the
following year. Soon, schools of fish began gathering in the electric fields
emitted by the buoys’ computers, which drew fishermen, some of whom scrapped
the equipment for copper wiring. Other sensors fell into disrepair after
funding cuts led to poor maintenance. In 2016, an earthquake in western
Indonesia, near Aceh, revealed that none of the buoys worked anymore.
I moved to Aceh seven years after the
tsunami, and one of the first things my hosts did after I arrived was show me
an escape route to the hills. Though an influx of international aid had mostly
rebuilt the city, I soon learned that its people—almost all of whom had lost
friends or family to the wave—had not recovered so easily. Even slight tremors
could trigger weeping flashbacks. When one of my friends disappeared—a
university student who had seen his mother and sister swept away—it was
eventually presumed that he had committed suicide. The Acehnese wisdom about
the danger lying beneath their feet was hard-earned.
Last Friday evening, about fifty miles
north of the Indonesian city of Palu, the United States Geological Survey
recorded a 7.5-magnitude earthquake along a fault six miles beneath the surface
of the island of Sulawesi. Experts have suggested that the earthquake triggered
a submarine landslide that forced colossal quantities of water into a long,
narrow bay, which channelled it directly at Palu, where the city’s three
hundred and eighty thousand inhabitants were enjoying the end of the week, many
of them preparing for a beach festival. A video posted to social media showed a
man atop a multi-story parking deck yelling desperately to people on the street
and beach below, “Run up here! There’s a tsunami! Run! Run!” All but a few
ignored his pleas, as three enormous waves—the tallest of which would later be estimated
at twenty feet—thundered across the nearby bay. The first wave swept a row of
single-story buildings off their foundations and swamped moving cars. As a
second wave reared, the man on the parking deck wept and screamed, “Heaven
forbid, Allah! Allah!” Then he turned and fled.
The earthquake and the tsunami reduced
large portions of Palu to wastelands of pulverized concrete and twisted metal
roofing. Because little heavy equipment was available, rescuers struggled to
move concrete slabs by hand as people trapped beneath begged for help. In the
days since, the death toll has leapt by hundreds daily, reaching more than
fourteen hundred on Thursday morning. Jusuf Kalla, the Indonesian
Vice-President, has warned that it could grow to thousands. International and
domestic aid has struggled to reach the suddenly isolated city, as its airport
runway and many of its inbound roads and bridges have been destroyed or
rendered unusable. In some neighborhoods, authorities have set up rudimentary
services, but elsewhere they have simply lost control: more than a thousand
inmates have escaped from three jails, one of which was set on fire, and
looters have attacked A.T.M.s with pickaxes. Reports have just begun to trickle
in from nearby villages, some of which, it seems, have been nearly obliterated.
Even as Indonesian authorities
struggled to respond to the aftermath of the disaster, they endured withering
criticism for failing to adequately prepare Palu beforehand. Indonesia’s
tsunami-warning system employs more than a hundred tidal-gauge sensors, but
none were close enough to Palu to pick up the localized wave. Authorities had
issued a tsunami warning for the area, based off readings from seismographic
sensors, but Gavin Sullivan, an associate professor at Coventry University who
studies disaster preparation and recovery in Indonesia, told me, “Many people
at the beach and on the [bayside] road had no idea the wave was coming at all.”
The city is equipped with tsunami sirens, but the earthquake had knocked out
their power, meaning that residents, such as the man on the parking deck, had
to shout warnings themselves. A text-message alert also system failed to
activate, because many cell-phone towers had already been destroyed. “There was
a chance for the Indonesian government to be better prepared for disasters like
this,” Louise Comfort, a disaster-management expert at the University of
Pittsburgh who leads a project to help Indonesia prepare for tsunamis, said.
“That makes the current devastation all the more heartbreaking.”
At a press conference, Sutopo Purwo
Nugroho, a spokesman for the Indonesian disaster-management board, said, “The
threat of disasters increases, disasters increase, but the budget decreases.”
(A 6.9-magnitude earthquake killed more than four hundred and sixty people on
islands southwest of Sulawesi, in August.) He acknowledged that he had found
out about the Palu tsunami through social media and TV.
“Indonesia is a developing country, and
it is difficult to allocate the resources, but we have to be ready for the
worst-case scenario,” Saut Sagala, a professor at the Bandung Institute of
Technology and a senior fellow at the Indonesian Resilience Development
Initiative, said. One dire possibility is an earthquake or tsunami striking the
greater metropolitan area of Indonesia’s capital, Jakarta, where about
twenty-eight million people strain an already overburdened infrastructure. “If
the government does not invest more on disaster risk reduction and increase the
preparedness of the communities, we will not be ready for these disasters,”
Sagala said. Among other things, he said, the government should work to educate
the population about disaster preparedness, retrofit buildings with
seismic-shock absorbers, stockpile resources, and use city planning to steer
people away from vulnerable areas. The Indonesian populations that are best
prepared for disasters, Sagala added, are those that have already suffered one.
Comfort, the University of Pittsburgh
professor, said that when she visited Aceh province after the 2004 tsunami she
was horrified to hear stories of “people running down to the beach to look at
all the exposed fish when the water drew back after the earthquake,” not
understanding that it was the first sign of an impending tsunami. “Of course,
they got caught in the oncoming wave.” But, though residents of Aceh now know
to flee for high ground after an earthquake, the Indonesian government seems to
have more quickly forgotten the lessons of the disaster. Comfort’s experience
with the 2004 tsunami inspired her, along with a team of American and
Indonesian researchers, to develop a new type of sensor to provide tsunami
warnings. Unlike the German buoys, which transmit data every fifteen minutes,
and so probably wouldn’t have been able to provide adequate forewarning of the
Palu tsunami even if they were operational, the new sensors would provide
updates within one to three minutes. And because they are situated on the
seafloor, they are protected from vandalism. The Indonesian government was
originally interested in using Comfort’s sensors, but the construction of a
prototype in western Indonesia had recently stalled for lack of funding, with
just a few more kilometres of undersea cable needed for it to be completed.
“There was a meeting a little more than a week before the tsunami,” Comfort
said. “But the relevant agencies decided they didn’t have the funding.”
Despite the ongoing tragedy,
Comfort still has hope that the Indonesian government can be more prepared for
the next disaster. The data from the system her team has developed could prove
helpful to other nations facing similar threats, for example, which might be
enough to convince the international community to share some of its costs.
“Tsunamis are a global risk,” she said. “Portions of the United States, like
Los Angeles and Seattle, as well as other cities, like Mumbai, in India, and
Darwin, in Australia, are just as vulnerable as Palu to tsunamis. As
populations worldwide concentrate in coastal cities, everyone needs to be
prepared.”
Doug Bock Clark is a writer
https://www.newyorker.com/news/news-desk/why-the-tsunami-in-indonesia-struck-without-warning
Indonesia earthquake
and tsunami:
How warning system
failed the victims
1
October 2018
There
were no sirens along the coast to alert residents to evacuate
Hundreds
of people have been killed and many still remain missing after a tsunami struck
the Indonesian island of Sulawesi on Friday, triggered by a powerful
earthquake.
A
tsunami warning was sent out - lasting just over 30 minutes - but it appears to
have drastically underestimated the scale of the tsunami that would follow. So
what went wrong?
What
actually happened?
A
7.5 magnitude earthquake occurred just off the island of Sulawesi at 18:03
local time (10:03 GMT) on Friday, triggering dozens of aftershocks.
Indonesia's
meteorological and geophysics agency BMKG issued a tsunami warning just after
the initial quake, warning of potential waves of 0.5 to three metres.
But
it lifted the warning just over 30 minutes later.
Palu
- a city in Sulawesi located in a narrow bay - was hit by waves as high as six
metres. The surging water brought buildings down and caused widespread
destruction. Hundreds of people had gathered for a beachfront festival and it
was was a scene of horror as waves powered over the beach - sweeping up
everything in their path.
Indonesia's
National Disaster and Mitigation Agency has said that most of the victims in
Palu were killed as a result of the tsunami.
Were
people aware there was a tsunami?
Many
critics have accused BMKG of lifting the warning too early, though the agency
says the waves hit while the warning was still in force.
BMKG
chairwoman Dwikorita Karnawati told the Jakarta Post that the decision to end
the warning was made after the agency received information about the tsunami,
including a field observation made by a BMKG employee in Palu.
She
added that the tsunami alert ended at 18:37, minutes after the third and last
wave hit land. She also said that there were no more tsunami waves after the
alert ended.
But
there's a bigger problem - though the alert was sent out, and according to the
communications ministry, repeated tsunami warnings were sent to residents via
text message - they might not have been received.
A
spokesman for the disaster agency said the quake had brought down the area's
power and communications lines and that there were no sirens along the coast -
which might have rendered the alerts essentially useless.
- On the ground report: Survivors guard rubble of Indonesian tsunami town
- In pictures: Search for Indonesia tsunami survivors
- Air traffic controller hailed as quake hero
One
video which has been widely shared on social media illustrates the chilling
consequences. It shows a man shouting cries of warning towards people alongside
the beach, who remain oblivious to a huge approaching wave.
Does Indonesia have a tsunami
early warning system?
Yes. Indonesia's tsunami early
warning system is currently made up of a network of 170 seismic broadband
stations, 238 accelerometer stations and 137 tidal gauges.
But according to BMKG's head of
earthquake and tsunami centre, the current system in place is "very
limited".
"Our [current] tools are
very lacking," said Rahmat Triyono, speaking to BBC Indonesian.
"In
fact, of the 170 earthquake sensors we have, we only have a maintenance budget
for 70 sensors."
However
we do know that the system did in fact pick up the tsunami - because a warning
was sent out - but what it failed to do was accurately gauge the scale of the
tsunami.
AFP Tsunami
buoys were given to Indonesia a decade ago to improve its early-warning system
- but none remain functioning
BMKG
revealed that the nearest closest tidal gauge to Palu was one that was well
over 200km away.
The
tidal gauge, which measures changes in sea level, only recorded an
"insignificant" 6cm (2.5in) rise. The tsunami height was estimated to
be less than 0.5m, BMKG said (in Indonesian).
"We have no observation
data at Palu. So we had to use the data we had and make a call based on
that," Mr Triyono told Reuters.
"If
we had a tide gauge or proper data in Palu, of course it would have been
better. This is something we must evaluate for the future."
Could
more lives have been saved?
It's
possible, as Indonesia does actually have a more advanced tsunami warning
system, including a network of 21 buoys which would have dispatched advance
warnings based on data gathered by deep sea sensors.
However
none of these buoys - donated by the US, Germany and Malaysia after the
devastating 2004 Indian Ocean tsunami that killed nearly a quarter of a million
people - are working. Some have been damaged by vandals and others have been stolen.
A
replacement system has been delayed due to a lack of funds.
Because
of this the BMKG predicts post-earthquake tsunamis using a modelling system
based on the earthquake depth and magnitude.
If
data were available from the buoys, "then our tsunami warning level would
be more accurate", Mr Triyono told BBC Indonesian.
AFP Indonesia's
geophysics agency BMKG admits its systems are lacking
The
latest disaster has highlighted the costs of Indonesia not having implemented a
more sophisticated early warning system.
BPPT,
the agency which manages the buoy system, has previously acknowledged that
government efforts have mostly focused on post-earthquake relief, while paying
"minimal" attention to pre-disaster anticipation.
But
was the tsunami expected?
Not
exactly.
This
is not the kind of earthquake that typically generates a major tsunami,
according to Prof Philip Li-fan Liu, vice-president of the department of civil
and environmental engineering at the National University of Singapore.
Tsunamis
are typically only generated when there is a large vertical displacement, he
said. But in this case, the tectonic plates were "rubbing against each
other horizontally, and when [that] ruptures it only creates a significant
horizontal movement and not much of a vertical movement".
Why
such massive waves were unleashed on Palu could perhaps be explained by the
nature of the bay itself.
According
to Dr Hamza Latief, an oceanographer at the Bandung Institute of Technology,
Palu has witnessed tsunamis in the past and when a tsunami hits its narrow and
elongated bay its impact is amplified.
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