Gempa Bumi di Malaysia

No accurate prediction of disaster, says expert

EARTHQUAKES cannot be predicted with accuracy and certainty.

Geophysics and Tsunami Department director Dr Mohd Rosaidi Che Abas says, however, that seismic agencies around the world are able to compile statistical estimates and probabilities of an earthquakes based on past records.

"But such forecast is very general covering a long period and a large area. It is arrived at by analysing the stress that builds along the fault lines of subduction zones."

This involves an oceanic plate sliding beneath either a continental plate or another oceanic plate. These areas are often noted for their high rates of volcanism, earthquakes and mountain-building.

"These are the areas where most of the earthquakes occur," he says.

The Malaysian National Tsunami Early Warning System (MNTEWS), which was established in 2005, monitors earthquakes and tsunamis in the region.

The centre within the Malaysian Meteorological Department monitors the phenomenon and issues alerts and advisories.

To monitor earthquakes in the region, a network of 17 seismic stations: seven in the peninsula, four in Sarawak and six in Sabah have been set up.

Rosaidi says through the network, MMD maintains a real-time monitoring of earthquake and tsunami occurrence in the region on a daily basis .

"The system also receives earthquake monitoring data from 34 stations overseas."

Sharing the ways MMD disseminate earthquake information to other government agencies, the mass media and the public, Rosaidi says it is done via SMS, a hotline, the Internet, phone and telefax within 15 minutes of an occurrence.

As for the implications of earthquakes, he said these range in intensity from slight tremors to great shocks which may last from a few seconds to as a long as several minutes.

"There may also be fore-shocks, which are usually small, and there may be many aftershocks which vary in intensity and last for days and sometimes even a month .

"Also, the impact of an earthquake depends on both the distance to the epicentre and the type of soil at the site. Hence the damage caused by an earthquake varies from one area to another depending on the factors.

"In a major earthquake, the energy released can be devastating and cause damage hundreds of kilometres away from the epicentre itself," he adds.

He says major earthquakes in the region usually occur in Indonesia and the Philippines, while tremors felt along the west coast of peninsular Malaysia originate from large earthquakes in the active seismic areas of Sumatra and the Andaman Sea.


Sarawak can expect minor shakes

THE northern parts of Sarawak are still at risk from tremors as they lie within the fault line.

The fault line runs all the way to Kota Belud in Sabah where tremors can go as high as six on the Richter scale.

Deputy Science, Technology and Innovation Minister Fadillah Yusof says, however, this is unlikely to occur.

"There was a tremor last year at 3.4 on the Richter scale. The highest recorded was 5.5 on the Richter scale in 2002. This is a normal occurrence. However, there may be stronger tremors, especially Kota Belud."

"We can't pinpoint where and when it will happen. There is no technology that has that capability.

"All we can say is northern parts of Sarawak will experience minor tremors from time to time and Sabah caost up to Kota Belud risk bigger tremors," says Fadillah.


Tremors lurkingunder our feet

It is common belief that Malaysia is immune to earthquakes. But tremors as low as 3.5 on Richter scale have been recorded in several areas in the country. KOI KYE LEE and DENNIS WONG talk to the experts

AT 7.47am on Jan 25, a mild tremor measuring 3.2 on the Richter scale was felt in Batu Niah near Miri in Sarawak.

The Malaysian Meteorological Department (MMD) said the epicentre was 26km from Batu Niah, 90km southwest of Miri and 99km northeast of Bintulu.

This is not the first time Niah felt such tremors.

Last year, a 3.3 Richter scale earthquake occurred in the same area. And Niah is not the only place in the country hit by mild tremors.

In October 2007, eight minor earthquakes shook Bukit Tinggi in Pahang.

The MMD said the earthquakes were due to the stabilisation process of the rock structure in the area.

The stabilisation process was due to rock movements from several major earthquakes in Indonesia like the ones in Aceh on Dec 26, 2004, Nias on March 28, 2005, Bengkulu on Oct 1, 2007, and Padang on Sept 30 last year.

The MMD says there is a very old fault line near Bukit Tinggi that has been dormant for more than 1.6 million years.

Historically, 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 five on the Richter scale.

The earthquakes were the result of reservoir-induced seismicity caused during an in-filling of the reservoir.

Ever since activities ceased in 1986, the area has been quiet. Induced seismicity can also be caused by the weight of water destabilising the region, or water seepage through cracks, which reactivated existing dormant fault lines.

The Engineering Seismology and Engineering Earthquake Research Group (E-Seer) of the faculty of civil engineering at Universiti Teknologi Malaysia says the nation is surrounded by part of the Pacific Ring of Fire which includes Sumatra, Sulu and the Philippines.

E-Seer researcher Mohd Zamri Ramli says earthquakes in surrounding regions like Sumatra, Sulu and the Philippines, can trigger the inactive fault lines in places like Bukit Tinggi and Batu Niah. The other existing fault lines in the country are located in Manjung, Mersing and Jerantut.

"In Sabah alone, tremors happen frequently in areas like Kudat, Lahad Datu and Tawau. Last year, we also experienced a tremor off Miri."

Zamri says even if a major earthquake does not occur in Malaysia, the effects of an earthquake in Sumatra could have dire consequences for the country. Citing an example, the 1985 earthquake that devastated Mexico City had its epicentre more than 350 km away.

Zamri says structural engineers must always consider the impact of seismic activity on high-rise buildings.

"We are within critical distance from one of the world's most active earthquake zones. Also, it is not earthquakes that kill people but the structures which collapse during quakes."

Universiti Malaya geology department senior researcher Dr John Kuna Raj says for Malaysia to experience a higher magnitude earthquake would depend on the location.

"The peninsula and Sarawak will experience at most low-magnitude earthquakes and ground shaking. As for Sabah, there is a possibility of low to medium magnitude earthquakes."