News: Unshaken complacency

The Star, Sunday October 11, 2009

Malaysia may not be as immune to earthquakes as is commonly believed. Earthquakes in neighbouring countries may trigger the inactive fault lines running in peninsular Malaysia, say experts.

MALAYSIANS think earthquakes will never occur in the country. But in reality, they do, with the most recent one with its epicentre in Manjung, Perak, occurring on April 29 this year.

In fact, Malaysia has a small history of earthquakes. The region around Sabah, especially around Ranau, Kudat and Lahad Datu, is no stranger to earthquakes, and according to a seismological expert, it is not uncommon for two or three to strike the area yearly.

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According to the Engineering Seismo­logy and Engineering Earthquake Research Group (E-Seer) of the faculty of civil engineering, Universiti Teknologi Malaysia, there is a possibility of a much larger earthquake occurring in Malaysia, especially if the earthquakes in Indonesia trigger the inactive fault lines running in peninsular Malaysia.

Mohd Zamri Ramli, a researcher from E-Seer, shares that an earthquake in the Indonesian region could trigger and re-activate the fault lines in the peninsula.

And even if a major earthquake does not happen in Malaysia, the effects of an earthquake in Indonesia could still have dire consequences for us. He points out the 1985 earthquake that devastated Mexico City which had its epicentre more than 350km away.

“What we are stressing is that we are within a similar critical distance from one of the world’s most active earthquake zones,” says Zamri.

The recent earthquake in Padang occurred 400km from Kuala Lumpur. The earthquake in Bengkulu (southern Sumatra) in 2000 happened 650km from Johor Baru and caused occupants of the now demolished Bukit Cagar flats to wake up in the middle of the night.

“The recent earthquake in Padang caused tremors for 10 minutes in the area around Johor Baru. That is something to be worried about. We do not know how our buildings will react to an earthquake of more than magnitude 8,” adds Zamri.

Che Noorliza Lat, a seismology and geophysics expert from the geology department, Universiti Malaya, says the devastation of an earthquake also depends on the underlying structure of the ground beneath the area.

She explains that Mexico City was built on a filled-up lake (Lake Texcoco). With its high water content, it was easily moved. She likens it to shaking a bowl of jelly as opposed to something solid.

“The jelly will wobble and shake but the solid piece will not wobble as much or at all,” she says, adding that it is possibly why some people in Malaysia felt the recent tremors and some did not.

Moving plates of rock

Going by the past, the peninsula is not as prone to tremors, but over a period of three years beginning in 1984, the area around the Kenyir Dam in Terengganu recorded about 20 tremors, the strongest of which registered at magnitude 5 on the Richter scale.

Bukit Tinggi in Pahang was hit by three earthquakes on Nov 30, 2007, followed by more than 10 separate events until the last in May 2008, but the strongest was a meagre 3.5 on the Richter scale.

There have been two more isolated earthquakes since, the one in Manjung, and another in Jerantut, Pahang, on March 27 this year, measuring 3.2 and 2.6 respectively.

It should be noted that the Kenyir earthquakes were reservoir-induced seismicity (RIS), possibly caused by the weight of the water destabilising the region, or water seepage through cracks, which reactivated existing dormant fault lines.

The other three locations on the peninsula are the only instances of naturally-occurring earthquakes in modern recorded history. While earthquakes do happen, it is not in a large and destructive scale as witnessed in neighbouring Indonesia, therefore the assumption that we are relatively safe is not far off the mark.

Noorliza explains that earthquakes happen because the earth’s crust is moving all the time.

“It is very dynamic. The earth is never settled and is always moving, constantly creating and destroying land.”

She says that the earth is covered with tectonic plates, which can be likened to ice sheets over a pool of water, and a fault line is where two or more plates meet.

“Tectonic plates are literally plates of rock which are moving. These plates move relative to one another, and sometimes they get lodged or stuck. They still exert force on each other, but do not move.

“Sometimes, the accumulated energy overcomes the friction and it breaks, and then we have an earthquake.

“In Malaysia, we do not get major earthquakes because we are not on the edge of a tectonic plate. We are on the Sunda Shelf, which is an extension of the Eurasia plate, so we should be pretty stable,” she says, but adds that nobody knows that for sure.

These plates have cracks on its surface, and these form minor fault lines and fractures.

“We are criss-crossed with fault lines, they are everywhere. We have the Mersing fault and the Bok Bak fault, for example, but these are all considered inactive as they do not move,” Noorliza says.

Not built for quakes

Dr Norhisham Bakhary, another researcher from E-Seer, says that with the exception of the Penang Bridge and KLCC, buildings or structures in Malaysia are not designed to resist the force of an earthquake.

This means that if an earthquake with a high magnitude occurred in Malaysia, there is a high possibility that most buildings would collapse.

Earthquakes at magnitude 2 will not be felt by humans, but at magnitude 3, some will feel it.

“It feels like a heavy lorry driving past. At magnitude 4, some light structures like huts may shake and fall, and at magnitude 5, some structures with no pilings may fail.

“However, if a magnitude 6 earthquake hits Kuala Lumpur, we are in trouble,” she says.

Dr Norhisham says that our buildings are only designed for a top or “normal” load and not for a lateral or side-to-side load which earthquakes cause.

He adds that for buildings to be able to withstand earthquakes, structural members have to be bigger in size, besides many other design considerations. This means more material is needed for construction, which translates into higher costs.

“Nobody wants to spend that much because they think it will never happen. I have spoken to building owners but no one really seems to care,” says Dr Norhisham.

Since buildings are not designed to sustain earthquake load, pre-earthquake assessment is the only way to evaluate their behaviour under earthquake loads. This assessment is done via computer simulation using a “finite element” method.

With this analysis, the behaviour of the building in an earthquake can be determined, and the critical part of the building identified for further action.

“If the building cannot withstand the load, then its structure will need to be strengthened,” says Dr Norhisham.

After an earthquake, the structural integrity of a building is compromised.

“The firemen can’t check the connections which are covered. Do we have to wait until something happens before we take any preventive action?”

He says that to ensure buildings are still safe after an earthquake, post-earthquake assessment is essential, which would first entail visual inspection. If needed, non-destructive tests can be conducted to identify unseen damage in structural members. Based on the results of the assessment, the rehabilitation process can proceed, if required.

Dr Norhisham emphasises that assessment should be done on buildings with large people capacity, such as schools, hospitals and government buildings.

Zamri says that Malaysia does not take into account the threat of earthquakes, unlike other countries.

“We do not have a design and construction code in relation to earthquakes. We need to conduct a lot of research in this area and create a hazard map by recording and analysing data in the long run,” he says.

Dr Norhisham says the Custom & Immigration Quarantine Complex (CIQ) has taken pro-active steps and have requested inspections on the complex.

“It will be costly but it has to be done,” he says, adding that E-Seer also received distress calls from Selayang Hospital as its authorities were unsure of what to do after the tremors.

Dr Norhisham points out that all it takes is for one beam to fail for a collapse to occur, citing the example of the Kuala Terengganu stadium roof collapse.

Noorliza opines that Malaysians do not need to be overly worried about earthquakes as there is no history of damaging earthquakes in the country.

“The likelihood is very small and so far, a magnitude 5 is the strongest,” she says.

However, she notes that recently, there has been increased seismic activity in the region and even in the country itself.

“There is a chance of an earthquake. We just do not know how big and where it will hit.

“I am not trying to cause panic, but it is a fact. I am not saying Malaysia is active seismically; it is only increasing in activity,” she says, adding that the public should be aware of what to do if an earthquake strikes.

“Those in high-rise buildings should be careful. Nothing bad will probably happen, but they should take precautions,” she says.

Noorliza advises them to exit the building orderly just in case it is only a foreshock – before the real one hits.

Zamri stresses that now would be a good time to educate the public about what to do in the event of an earthquake.

“We must have a drill for earthquakes, just as we do for fires,” he says, adding that in Japan, people are taught not to run but to seek shelter under a table or bed and with a bottle of water and their handphone.

Source: http://thestar.com.my/news/story.asp?file=/2009/10/11/focus/4882460&sec=focus