Powered By Blogger

Montag, 31. Dezember 2018

TSUNAMIS IN INDONESIA: ANY LESSONS LEARNED?



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.


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.
Copyright © 2018 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.




Keine Kommentare:

Kommentar veröffentlichen