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Deadly Earthquake Jolts Sumatra, Tsunami Fear Recedes

Sean Markey
National Geographic News
March 28, 2005
 
A magnitude 8.7 earthquake struck near the Indonesian island of Sumatra earlier today. The shock initially raised fears that another deadly tsunami could ripple across the Indian Ocean in the wake of killer waves that devastated the region last December.

While those concerns did not materialize, at least 320 people have died and hundreds of homes were damaged or destroyed on Nias, an island 75 miles (120 kilometers) off the Sumatran coast, according to government sources.

A. Nainggolan, the deputy police chief of Gunungsitoli, the main town on Nias, described the quake as "massive," the Reuters news service reported.

Elsewhere, the quake knocked out electrical power and sparked panic in Banda Aceh, on the northwestern tip of Sumatra. The city was hit hard by record earthquake and tsunami damage three months ago.

Similar scenes of alarm were reported in other Pacific regions, where the nightmare of the December 26 tsunami that left more than 300,000 dead or missing remains fresh.

In Thailand government officials issued warnings to people in six provinces to flee coastal areas in anticipation that a tsunami might follow today's quake. Thousands are said to have heeded the call, evacuating beaches and shorelines as they fled to higher ground.

As of press time, no casualties had been officially reported there.

In Malayasia fire alarms sounded in hotels and apartment buildings as residents were urged to evacuate buildings, the Associated Press reported.

Jessie Chong lives in Kuala Lumpur, the Malaysian capital, which is located 330 miles (535 kilometers) from the epicenter of today's quake. Chong told the news agency, "I was getting ready for bed, and suddenly, the room started shaking. … I thought I was hallucinating at first, but then I heard my neighbors screaming and running out."

"Fraternal Twin"

According to the U.S. Geological Survey, today's quake began at 11:09 p.m. local time. Its epicenter was located about 18 miles (29 kilometers) beneath the Indian Ocean and 125 miles (205 kilometers) west of Sibolga, a city on the northwest coast of Sumatra.

Tremors from the quake, which some reported lasted two minutes, were felt in Indonesia, Malaysia, Singapore, and as far north as Bangkok, Thailand, the agency said.

Speaking at a press conference in Pasadena, California, one USGS expert said today's earthquake appeared to be the "fraternal twin" of the magnitude 9.3 temblor that rumbled in December.

Shortly after the latest shock, U.S. National Oceanic and Atmospheric Administration officials issued a warning that residents living in coastal areas within 600 miles (1,000 kilometers) of the quake's epicenter should evacuate.

Quake Predicted

For weeks seismologists have advised that another earthquake along the same fault that triggered December's deadly quake and tsunami was likely.

In a study published earlier this month in the science journal Nature, one research team predicted that an earthquake as strong as magnitude 7.5 could occur along the Sumatra Fault, but they could not say when.

John McCloskey, a seismologist at the University of Ulster in Northern Ireland, led the study. In an interview with National Geographic News two weeks ago, McCloskey said: "People believe lightning never strikes twice in the same place. Earthquakes do.

"Earthquakes cluster in space and time. When you get an earthquake, you are more likely to get another, and our calculations show the stress interaction [in South Asia] is very high."

The latest shock occurred in a zone prone to cataclysmic earthquakes, where a number of pieces of Earth's tectonic crust jostle against, over, and under one another.

Double Trouble

Sumatra, in particular, is prone to two different types of earthquake activity.

The first occurs along the Sumatra Fault, a strike-slip fault akin to California's San Andreas Fault, where two smaller pieces of Earth's crust grate and slide against each other, shoulder to shoulder.

The second occurs along a subduction zone known as the Sunda trench. Passing within 125 miles (200 kilometers) of the west coast of Sumatra, the 3,400-mile (5,500-kilometer) fault stretches from Myanmar (Burma) toward Australia.

Along the trench, two puzzle pieces of the Earth's tectonic crust—the Indian and Australian plates—are diving beneath a third tectonic plate, known as the Burma plate—a process called subduction.

It was there that a magnitude 9.3 earthquake trembled on December 26, 2004. The quake moved trillions of tons of rock along hundreds of miles of fault, making it the largest recorded earthquake in 40 years.

As the seafloor shifted, a huge volume of water was displaced, creating the tsunami that traveled at jet speed and lashed the coasts of 11 nations in Asia and Africa within hours.

According the U.N., more than 300,000 people were soon killed or lost. Nearly 100,000 people died in Indonesia, the agency said, and over a million people in affected nations were displaced.

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