Just a matter of time before Big One hits, warn experts

Amresh Gunasingham, Straits Times 1 Oct 09;

THE earthquake which hit Sumatra yesterday was one of the worst this year, said a top geologist.

And the escalating intensity of quakes in the region in recent years will eventually be followed by a massive quake. This will be on the scale of the one which caused the 2004 tsunami, said Professor Kerry Sieh, 58, an expert in seismology.

'The Sumatran earthquakes of the past 10 years are really quite unusual,' said Prof Sieh, director of the Earth Observatory of Singapore at the Nanyang Technological University.

Nothing as intense or energetic has been seen in 200 years, he said.

Yesterday's earthquake was particularly worrying, explained Prof Sieh, because it was right on the edge of a 400km rock patch - known as the Sunda megathrust - which is under great stress from the movement of two tectonic plates constantly grinding against each other beneath the sea.

'This patch is where we think the next great earthquake will be generated within the next three decades,' he said.

The magnitude 7.6 quake stuck the city of Padang in Sumatra's west coast, a belt of intense seismic activity known as the 'Pacific Ring of Fire' - one of the world's most active faultlines.

Geologists have long said Padang may one day be destroyed by a huge earthquake. Since 2005, it has been hit by more than five major earthquakes measuring 6.5 or higher on the Richter scale.

Geologist Danny Hilman Natawidjaja of the Indonesian Science Institute told The Straits Times that a stronger quake could be devastating for Padang.

'We are very worried...that the accumulated energy in one quake of magnitude 8.9, for example, could see a tsunami reaching 7m high hitting the coast.'

Such a tsunami would affect more than a million people living along the coastline.

He added that the decade-long sequence of quakes meant government officials were making adjustments to infrastructure and educating the people in preparation for the inevitable stronger earthquake and tsunami.

Indonesian Meteorology and Geophysics Agency technical chief Suharjono said that up to 6,000 quakes of a magnitude over 4.5 hit Indonesia every year.

However, researchers are unable to pinpoint exactly when the 'big one' will occur.

Said senior seismologist D. Srinageswar of India's National Geophysical Research Institute: 'Prediction of a quake in time is not possible. The process will need data going back hundreds or even thousands of years.'

While yesterday's earthquake caused major damage in Padang, its residents were spared a tsunami because the quake was not intense enough and its epicentre was too deep below the sea's surface.

Oceanographer Pavel Tkalich, principal investigator at the National University of Singapore's Tropical Marine Science Institute, said that water levels had been raised only 30cm yesterday, and that it would take an earthquake of at least 8.0 in magnitude to cause a tsunami stretching across the region.

Additional information from Agence France-Presse

Sumatra quake: Tremors felt in Singapore and KL
Teh Joo Lin in Singapore & Elizabeth Looi in Kuala Lumpur
Straits Times 1 Oct 09;

IT WAS a regular day at work, until accountant Kelvin Ng's office began to sway.

The 26-year-old ran nine flights down from his Bencoolen Street building to the road outside.

'It was so bad it gave my friend a headache,' he said.

He was among thousands in Singapore and Malaysia who had a fright when they felt tremors in the wake of the 7.6-magnitude earthquake that struck off Padang, Sumatra.

For up to two minutes, people in Singapore reported seeing curtains sway, grilles rattle and chairs shake in buildings from Choa Chu Kang to Changi.

Workers and residents streamed out of some buildings in areas such as Raffles Place and Changi, and officers from the Building and Construction Authority were out inspecting buildings last night.

The authorities received some 170 calls about the tremors, but no casualties were reported.

The police said there was no cause for alarm.

'Buildings in Singapore are designed to established building codes and are sufficiently robust to withstand tremors caused by distant earthquakes,' said a spokesman.

The Foreign Affairs Ministry said last night that it is monitoring the situation, but so far there were no reports of Singaporeans affected by the earthquake.

In KUALA LUMPUR, the landmark Petronas Twin Towers, the 28-storey Wisma IMC office building which houses the New Zealand High Commission, and the JayaOne Complex shopping mall in Petaling Jaya were among the buildings affected.

Media relations manager Dalilah Ibrahim told The Straits Times that she felt dizzy and disorientated when her office in Cyberjaya, Malaysia's equivalent of Silicon Valley, shook for about 10 seconds.

'I could see my Hari Raya greeting cards shaking on the wall,' she said. 'We were asked to evacuate the building for about 15 minutes although my office is on the ground floor.'

Bank officer Delren Douglas, 39, said he could feel the tremors in his first-floor office.

'It lasted for about a minute and I could see the plants in my office were swaying,' said the Klang-based worker.

People in Penang also felt the tremors.

A factory executive in the northern state said her third-floor office shook for more than a minute.

'My colleagues and I were dizzy and nauseous after the tremors,' she said. 'It all happened so quickly.'

The Pacific Tsunami Warning Centre issued a tsunami alert for Indonesia, Malaysia, India and Thailand, but withdrew it at 7.30pm last night after the quake generated no significant waves.

The Malaysian Meteorological Department did not issue a warning as it believed the waves would not reach Malaysia, but the department would continue monitoring the situation, The Star reported.

The devastating tsunami of December 2004 hit Penang and Kedah following a powerful 9.6-magnitude earthquake in Indonesia.

Tremors in various parts of Singapore following quake in Indonesia
Asha Popatlal, Channel NewsAsia 30 Sep 09;

SINGAPORE: Singaporeans island-wide literally felt the earth move under their feet on Wednesday evening as tremors shook various parts of the island - from Redhill in central Singapore to Pasir Ris in the northeast.

This came after a powerful earthquake of magnitude 7.6 hit Indonesia.

Singapore's Meteorological Services confirmed that the earthquake struck at about 6.15pm on Wednesday in the waters off Southern Sumatra, about 530 kilometres from Singapore.

Minutes later, MediaCorp's news hotline started ringing as Singaporeans reported feeling tremors that lasted anywhere between 30 seconds and a few minutes.

The Police and SCDF said they received more than 150 calls about the quake.

Videos sent in by viewers showed chandeliers swaying, as were other objects.

The calls came from across the island - Ang Mo Kio in the central north, Marine Parade in the east, Punggol in the northeast and Raffles Place in the central business district.

Callers said that some workers in the Suntec area and Changi Business Park were evacuated.

One man said: "There were a lot of office people on the roadside. We felt it for about five to ten minutes." Others said their neighbours were screaming and shouting.

Rajakumar Choppa who works at Expo Changi Business Park, said: "Around 6pm, we felt some kind of a building shake. I felt it three times actually and then we all stood up and rushed downstairs because there was some fire alarm in the building.

"When we got downstairs, there was a crowd. We were all watching and not knowing what was happening. I was able to see the building literally shaking."

Callers also reported jams in the Causeway area as the bridge was shaking.

Experts MediaCorp spoke to said the situation was bad.

Professor Kerry Sieh, professor of Geology, Earth Observatory of Singapore, NTU, said: "It's definitely getting worse. The earthquake sequence began in 2000 with a 7.9 about 800 km away from the south of Singapore. You haven't felt this big of a sequence of earthquakes that is many large earthquakes for at least 175 years."

A tsunami warning was initially issued after the quake but later withdrawn. - CNA/vm


What The Police Say
Today Online 1 Oct 09;

The public is advised that there is no cause for alarm. Buildings in Singapore are designed to established building codes and are sufficiently robust to withstand tremors caused by distant earthquakes.

Should cracks or other structural defects develop, residents or occupants in public housing estates should call the HDB's Essential Maintenance Service Unit's 24-Hour Hotline at 6275 5555 or 6354 3333. Those in private buildings should call the Building and Construction Authority at 6325 7191 or 6325 7393.

Panic across Singapore
Leong Wee Keat, Today Online 1 Oct 09;

SINGAPORE - The scene "felt like a Jurassic Park moment", according to one Shenton Way executive. The workday was winding down at around 6.15pm, when Mr MH Farik's chair began shaking. Then, the water in his mug began to slosh around.

As more items in his office started shaking vigorously, first giddiness, then panic set in among some colleagues. They abandoned their 13th-storey office at Keck Seng Tower, near Cecil Street. When Mr Farik got to the ground floor, "hundreds" were already downstairs. "It felt really scary to see items around us shaking so badly," he said.

Across Singapore, many had similar tales as they felt the tremors from the earthquake off Sumatra island 590km away.

Hundreds of callers to the MediaCorp and emergency hotlines reported tremors as far north as Woodlands, Sembawang, Yishun and Choa Chu Kang, sharing accounts of how fans, chairs, chandeliers, fish tanks and ceiling lights were swaying. Some even heard neighbours screaming and running down the stairs to escapef from the building.

Typically, reports of tremors felt tend to be limited to the southern parts of Singapore. But those who experienced yesterday's rumbles said the after-shocks felt stronger and lasted longer than in previous tremors.

Instead of just "one to two minutes", Marine Parade resident Wendy Sng said these lasted "three to four minutes". "My wind chime also sounded loudly - only thing was, there wasn't any wind blowing," added the retiree.

The last time after-shocks were reported here was in February last year, when the police received 60 calls from the public. And the last time the business district saw scenes similar to yesterday's was in Sept 2007.

Mr Aaron Yeo, who works in the Suntec area, was among 500 office workers who vacated his building even though there were no public announcements. "We were all sitting at our desk and then we felt some giddiness, and when we stayed still, we realised that it wasn't us shaking but the whole building."

In the housing estates, the sights were of shaking lights, swaying mid-autumn festival lanterns and "a loud cracking sound", in the words of Woodlands Crescent resident YL Chua, who had just arrived home from work. "The last time tremors felt so strong was during the Asian Tsunami (in 2004)," he added.

Over at Potong Pasir, Ms Tan Su Yan was chatting on the phone when she felt the tremors. She and her neighbours ran out of their homes and gathered at an open field. "I felt giddy even sitting in the open field," she said.

Professor Kerry Sieh, head of the Earth Observatory of Singapore at Nanyang Technological University, warned that the earthquake situation around the Pacific Ring of Fire is getting worse.

The 40,000-km stretch across the Pacific Ocean has a continuous belt of active volcanoes and experiences frequent tectonic plate movements.

"The earthquake sequence began in 2000 with a 7.9 (magnitude) about 800km to the south of Singapore," said Prof Sieh. "You haven't felt this big a sequence of earthquakes - that is, many large earthquakes - for at least 175 years."