By Philip Bethge
Nils Goseberg is very worried about the Siti Nurbaya Bridge in Padang. The 80-meter (262-foot) bridge spans the Arau River and anyone fleeing a tsunami would most likely need to cross it.
Goseberg, who works at the Franzius Institute of Hydraulics, Waterways and Coastal Engineering in the northern German city of Hanover, faces a problem that seems borderline absurd: How to evacuate Padang, a city of 800,000 people, in just 20 minutes?
The tsunami that hit South East Asia in 2004 killed over 200,000 people.
The project being conducted by the Hanover experts is part of a concerted action by German scientists to deprive Indian Ocean tsunamis of some of their destructive potential. The core of the emergency program is the German-Indonesian Tsunami Early Warning System, or GITEWS. A trial run of the system is set to begin in Jakarta next Tuesday.
On Dec. 26, 2004, an earthquake that measured 9.3 on the Richter scale shook the ocean floor off the coast of the Indonesian island of Sumatra. The resulting tsunami hit the coast with such force that 210,000 people were killed. Many wonder anxiously when the next giant wave will roll across the region's coasts.
According to an article published in the journal Nature last week, the shocked world public was hardly witnessing a one-of-a-kind geological event in late 2004. In two studies, paleo-tsunami researchers examined the evidence left behind by similar giant natural disasters in the earth's history. The research teams from Thailand and the United States found sand deposits far away from the coast that could only have been put there by enormous tsunamis. They concluded that monster waves have careened across the region three times in the last 2,000 years.
The job of detecting the next wave in time now falls to the Germans. After the horrific 2004 tsunami, they donated 45 million ($57 million) for an early warning system, a move that brought them little more than widespread derision at first.
Experts in Japan and the United States claimed that the German tsunami neophytes had too little experience with monster waves. The Germans faced malicious criticism when early measuring buoys were torn from their moorings and ended up adrift off the coast.
The critics have grown silent since then. "The design of the system seems sound," says Vasily Titow, a tsunami researcher in the United States. And Costas Synolakis of the University of Southern California has almost paternal words of praise for the Germans, saying: "While I was one of the early critics, I have to admit that German scientists have made incredible strides towards developing the system."
In fact, the GITEWS team has developed a number of clever methods:
* Seismometers record any movement in the rupture zone off the coasts of Sumatra and Java.
* GPS stations on land also measure the movement of the tectonic plates. Using the two systems, scientists can quickly determine the magnitude and epicenter of a quake, as well as the direction of fracture, which enables them to pinpoint the origin of a possible giant wave.
* Measuring buoys and pressure sensors detect a monster wave directly in the ocean when it is still far out to sea.
* Tide gauges near the coast show exactly where the wave will crash against the coastline.
A monster wave follows every earthquake. But, says Weber, only a "snapping in the crust" leads to a tsunami. To avoid false alarms, the experts also observe the ocean itself. Three measuring buoys brimming with electronic equipment are now bobbing in the high seas off Sumatra. The equipment is capable of measuring water levels with a precision of five centimeters. The buoys are raised slightly when a tsunami passes beneath them, which sets off the alarm.
"Tsunamis only become very tall near coastlines," explains project director Lauterjung. "They are long and flat out on the high seas." Nevertheless, the technology can detect the pattern of a tsunami.
A map of Indonesia hangs in Lauterjung's office in building A40 at the GFZ headquarters on Potsdam's Telegrafenberg Hill. Strips of colored tape mark the components of the tsunami system, which is really a way of listening in on the planet's inner workings.
The tightly woven monitoring network has only one goal: speed. If there is an earthquake in the Sunda Trench, for example, the Indonesians have only a few minutes to react. "The subduction zone is so close to the coast that we have an extremely short early warning window," explains Lauterjung.
In the 2004 disaster, for example, in took only 15 minutes from the time of the earthquake for the resulting wave to inundate the city of Banda Aceh. According to Lauterjung's estimates, Indonesians have an average of 20 minutes to respond to a tsunami warning, which is "very little time to get to a safe place."
According to rules established by the Indonesian president, GITEWS is supposed to spit out an initial "reliable warning message" after five minutes. To avoid mass panic, details are critical. Where exactly will the wave hit the coast? How high will it be? Which cities and towns must truly be evacuated?
The data from the various measuring systems is compiled in a warning center in Jakarta, where it is used to simulate tsunamis in a high-powered computer. Then the software selects the most likely scenario from a current library of about 1,000 tsunami models. "It already takes less than a second to get a result," explains Jörn Behrens, a mathematician with the Alfred Wegener Institute in the northern German port city of Bremerhaven.
There are still problems. For instance, the measuring buoys are plagued by a purely human problem. "The fishermen tie their boats to the buoys," says Lauterjung, "and when that happens, unfortunately things break." The scientists have already had to tow one of the three-and-a-half-ton devices back to Jakarta for repairs.
But the scientists' biggest concern is the last step in the cascade of warnings. Even if the threat is successfully recognized, how are people made aware of it? And how will they react?
The choreography is already firmly in place. The report of an incoming tsunami would be announced on radio and television, through loudspeakers at mosques, via fax machines and text messaging. But even these steps take practice. In July 2006, an earthquake off Java triggered a tsunami. Even though the geologists issued a warning, the government sought to avoid "unnecessary panic." Later on, Science Minister Kusmayanto Kadiman said that 400 text messages had been sent -- to government representatives. But that was where the news of the impending disaster ended, and 600 Indonesians died.
"People simply have to be better prepared and trained," says Lauterjung, undaunted. He envisions providing instruction in elementary schools, advising local politicians and training technicians. The German Society for Technical Cooperation (GTZ) has already begun local programs to prepare the population for the next tsunami.
There is no doubt that there will be another one and the city of Padang is considered especially vulnerable. There were earthquakes north of the city in 2004 and 2005, and south of Padang in 2007. But the ocean floor directly off the city's coastline remained calm. As Lauterjung explains, pressure in the rock there has risen to worrisome levels. "We are already expecting a magnitude 8 to 8.5 earthquake."
Nils Goseberg, the engineer from Hanover, will have to hurry if he hopes to do anything to help the citizens of Padang. "Where are the bottlenecks that will slow down an evacuation? Which bridges are too narrow? Where would it make sense to build new roads that would quickly divert the water into the interior?" These are the kinds of questions Goseberg is asking.
But sometimes even Goseberg feels doubtful. In the end, anyone hoping to warn the Indonesians about tsunamis has the Indonesian mentality to contend with.
"During last September's earthquake, I got a firsthand look at how the people reacted," says Goseberg. His devastating conclusion? "They all run down to the beach to see what the water is doing."
Translated from the German by Christopher Sultan
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