It was a through-the-looking-glass moment for Chris Goldfinger, sitting in a meeting about Sumatran earthquakes on a recent Friday afternoon in Chiba, Japan, on the outskirts of Tokyo. The floor started heaving as if a switch flipped. That terrible shaking turned out to be the magnitude 9.0 Sendai temblor, tsunami-maker and devastator.
"We felt pretty safe," says Goldfinger, director of Oregon State University's Active Tectonics and Seafloor Mapping Lab, "but, oddly, still had time to run outside and ride through four or five minutes of mainshock. That was a very long time for the Earth to feel like the ocean."
At that point the ocean itself was already rearing up from its cracked floor to drown the coast 290 kilometers to the northeast. One month later, Japan is still in crisis.
Even so, one finer point in the wake of that horrible day will be what science can do to improve the odds—to give better, faster tsunami warnings. For Goldfinger—still rattled in Chiba—warning systems are a bill of goods, a chimera. "The earthquake is the warning," he says, describing a "near-field" event like Sendai where the temblor is very close to the coast. "Warning systems have been greatly oversold by those who created them."
One such creator, physicist Jörn Lauterjung, disagrees and draws a different lesson. Japan has decades of planning experience and an established early warning system. On March 11, a tsunami warning went out within three minutes to the three most-affected provinces, providing about 10 minutes to react. Instead of 25,000 dead and missing, with waves humbling nine-meter high seawalls, Lauterjung figures it all could've been much worse, although he and others even see room for new research, for improvement.
A German in Indonesia
Lauterjung's reference point is the 2004 Indian Ocean tsunami which hit Indonesia and southern Asia. Some 250,000 people died that day. There was no early warning.
After that event the German government in Berlin pledged $60 million to build such a system: engineering, data processing and geologic experience were readily available. Lauterjung's team at the Helmholtz Association's Research Center for Geosciences (GFZ) worked with a dozen other German science labs, private tech companies and international research institutions on the new system. It went online in 2008. Researchers have since been tweaking and optimizing it as well as educating system users, operators and the local population. The Indonesians are now poised to take over: Lauterjung was in Jakarta a couple weeks ago handing off the keys to the network.
The volcanic, earthquake-prone Sunda Arc, which forms the Indonesian islands of Sumatra and Java, lies along the boundary of two eastern Eurasian tectonic plates, putting Indonesia at high risk for "near-field" tsunamis like the one at Sendai. In order to issue an early warning, a precipitating earthquake must first be detected; alarm data is then transmitted to the Jakarta main warning center in the Indonesian capital. The resulting wave height and arrival time is determined, evaluated and retransmitted to a wide variety of potentially affected locations along the rough jungle coast of Sumatra. Warnings must be accurate—every false alarm erodes confidence in the system—and very rapid.
The baseline goal is to issue initial warnings and information to the public within five to 10 minutes of detecting risk. Even then, the local population must be notified and know how to respond. It is a tall order.
Hardware and software
The system has a set of main components and one master: time. The GFZ design connects four basic units, including seismic stations; a buoy and pressure-plate system to monitor wave motion; a set of coastal tide gauges; and a real-time GPS lattice network overlaying it all.