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Experts: Okinawa ‘well overdue’ for quake

CAMP FOSTER, Okinawa — With the memory of Japan’s devastating disaster still fresh, scientists are warning of a possible repeat on Okinawa, saying the island is overdue for a mega-earthquake that could send a tsunami over coastal communities and U.S. bases where thousands of Americans live and work.

Mindful of the 18,000 killed when the March 11, 2011, earthquake spawned a tsunami and a nuclear disaster, the Marine Corps has unveiled a new tsunami warning system and evacuation plan for Okinawa designed to clear out low-lying bases before a deadly wave strikes, though coordination with nearby Japanese communities remains a work in progress, according to emergency management.

A major earthquake on Okinawa is “well overdue and can happen at any time,” said Takeshi Matsumoto, professor of earth science and disaster prevention at the University of the Ryukyus. Matsumoto sits on a panel of six university seismic experts who re-evaluated the tsunami danger for the Okinawa prefectural government following the 2011 disaster.

The public belief that Okinawa is immune to such events is a myth, Matsumoto said.

The island straddles 13 active faults and sits along the edge of the Eurasian and Philippine Sea tectonic plates in the Pacific Ocean.

As one plate slides under the other, energy builds up, causing increasing numbers of small quakes, Matsumoto said.

The Okinawa Meteorological Observatory has observed more than 870 tremors over the past month, most of which were imperceptible without monitoring equipment.

Meanwhile, the shifting plates are causing the growth of fissures in the East China Sea, putting increasing pressure on an island that is already crisscrossed with active faults, Matsumoto said.

“At some point, the friction will reach a point where the accumulated energy can no longer be absorbed,” he said. “Under these circumstances, a massive earthquake is inevitable.”

A big earthquake is likely to cause a tsunami, though the deadly waves are rare.

The 2011 disaster is thought to be an event that happens just once every 1,000 years, Matsumoto said. That tsunami scraped away 9,000 acres of coastal land, completely wiping whole communities off the map and leaving vast stretches strewn with crushed homes and jumbled vehicles. Two years later, the area is still trying to recover.

The island of Ishigaki, near Taiwan, suffered a massive tsunami that killed about 12,000 in 1771. The island of Okinawa has no record of a large tsunami during the past millennium, Matsumoto said.

A mega-quake and tsunami would likely devastate a number of U.S. military bases along with much of the densely populated central and southern coasts, according to newly updated tsunami flood maps released in February by the prefectural government.

A 16-foot tsunami could engulf sections of camps Foster, Lester and Schwab, as well as the popular American Village Shopping district, the U.S. Navy base at White Beach and the Okuma Recreation Center, the maps show. The water could be much higher — the tsunami on Japan’s northern coast rose 30 to 40 feet, according to various accounts.

Facilities on much higher ground, such as sprawling Kadena Air Base and Futenma Air Station, are unlikely to be affected, the flood maps show.

The new assessment has underscored the Marine Corps’ effort to upgrade its tsunami plan since the 2011 disaster. Immediately afterward, the service approached Michael Lacey, regional installation emergency manager for Marine Corps Installations Pacific.

“They said, ‘Mike, how prepared are we for this?’ ” Lacey said. “I said the reality is we are not. … Our eyes were open at that point.”

In February, the service, which owns most of the at-risk coastal bases, began routine testing of a new system of sirens that will alert every facility on the island simultaneously if a tsunami alert is issued.

In the past, each Marine Corps base was responsible for calling its own warning. Now, the alert system is linked through the central provost marshal’s office on Camp Foster, which continually monitors for updates from the Japan Meteorological Agency and its tsunami warning system, Lacey said.

The alarm can be sounded within minutes of an earthquake. Time is crucial — a mega-quake along nearby fault lines could send a wave over coastal bases in 20 minutes, he said.

Those on base are supposed to walk to higher ground. The Marine Corps signed an agreement last year to open its gates so Japanese residents along the coast can evacuate on foot through bases.

“We’ve exercised this stuff, and it works great,” Lacey said. The most recent test evacuation was Feb. 23.

Lacey said work is still needed to fully coordinate with local Japanese communities when an off-base evacuation is called. The military hopes to get more accurate notice of when hundreds or thousands of evacuees will begin reaching military gates.

There are also plans to upgrade the blue tsunami warning signs at bases with more detailed safety information, he said.

“We’ve made significant progress; however, I think we still have a long way to go,” Lacey said. “I think everybody is doing their diligence.

“We all learned lessons” from the 2011 disaster, he said.

tritten.travis@stripes.com
sumida.chiyomi@stripes.com
 

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