A pair of aftershocks rattled the South Pacific island nation of Tonga on Friday but caused no damage or injuries, a day after a large quake exposed alarming cracks in a tsunami warning system.
A magnitude 6.0 and a magnitude 5.4 aftershock hit the same region of Tonga, the U.S. Geological Survey reported, but there was no sign of any damage in the capital and no tsunami warnings were issued.
The Hawaii-based Pacific Tsunami Warning Center said Tonga and four other Pacific nations were inadvertantly left off a list of areas most at risk of being hit by a tsunami following the 7.8-magnitude earthquake Thursday.
Officials had earlier said Tonga, which was closest to the epicenter, apparently did not receive a tsunami alert because of a power failure.
But Gerard Fryer, the center’s acting director, told The Associated Press that the five nations were not given tsunami “warning” or “watch” status on the initial alert. Fiji and New Zealand were alerted. He said a glitch in the center’s computer database caused the problem, and a staffer failed to catch the omission in a rush to get out the alerts.
A second bulletin issued at 6:31 a.m. from the Hawaii center, 49 minutes after the first alert, correctly included Tonga, Niue, American Samoa, Samoa, and Wallis-Futuna as countries also under the tsunami warning, he said.
By then, it would have been too late if a destructive tsunami materialized — it would have already hit Tonga, Niue and American Samoa.
The Honolulu-based Pacific Tsunami Warning Center lifted the alert within two hours, after a wave of less than 2 feet was recorded.
The failings raised troubling questions about how alerts issued in Hawaii reach remote communities scattered across the earthquake-prone Pacific.
“If people don’t get it (the warning), it’s not worth anything, but we don’t have people in every country who can help keep their sirens running and their power running. It’s frustrating,” said Barry Hirshorn, a geophysicist at the warning center in Hawaii.
Mali’u Takai, deputy director of Tonga’s National Disaster Office, told The Associated Press that the failure could have proved deadly, as the epicenter of the earthquake was just 95 miles south of the Tongan island of Neiafu.
“Nobody got a warning through the emergency satellite system in our meteorological office,” Takai said. “Judging by the location of the epicenter, we would have been caught out without any warning at all because of the system’s malfunction.”
The center has made corrections since Thursday’s error, Fryer said, including the implementation of an automatic second check built into software.
“That error will not happen again,” he said.
On Dec. 26, 2004, the most powerful earthquake in four decades — magnitude 9.0 — ripped apart the Indian Ocean floor off Indonesia’s Sumatra island, spawning giant waves that sped off in all directions.
The disaster led to an urgent review of warning systems in 23 countries, which will participate in a simulation in two weeks to test their readiness if a tsunami is unleashed. The exercise was not expected to involve any simulated evacuations.