"Part of a Chain"
The 2004 earthquake off Aceh province in northwest Sumatra (see map of Indonesia) had a magnitude of 9.2, making it the most powerful temblor in four decades.
It triggered a tsunami that killed 230,000 people in 12 Indian Ocean countries, with more than half the victims in Indonesia.
Three months after the tsunami, a magnitude 8.6 quake farther down the fault line killed a thousand people. Then in September last year, an 8.7 quake opposite Bengkulu province damaged thousands of homes, killed about 25 people, and sent a ten-foot (three-meter) tsunami crashing into nearby coastlines.
Last Wednesday a magnitude 7.4 quake killed three people and damaged scores of houses.
"They are best seen as part of a chain that began in 2004," said Dr. Fauzi, a top scientist at Indonesia's National Earthquake Center. "The stability of the fault has been disturbed," said Fauzi, who goes by a single name.
Since the Indian Ocean tsunami, Indonesia has spent millions of dollars to establish a nationwide tsunami warning system, but there are still only a few warning sirens in Sumatra's threatened western coast and other beach areas.
Officials and residents of the two populous cities of Padang and Bengkulu said no sirens sounded following the recent earthquakes despite warnings issued by the country's Meteorology and Geophysics Agency.
"We don't have such equipment," said Suyud, an official at Bengkulu's Meteorology and Geophysics Agency. "If there were tsunami warnings issued it was only government officials who knew that from text messages on their cell phones."
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