The power of Earthquakes!!
Posted by ZuLaiShah in Information/Knowledge, World Talk on 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.
According to the Engineering Seismo logy 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.
For more information, please refer to The Star Online.
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