NST 2010

Tremors lurkingunder our feet

NST NEWS 2010/02/02

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.”