The Unpredictable Earth Tremors
By Dileesha Abeysundera
The walls of my house cracked and the tiles also broke as a result of the vibrations caused by what seemed to be a plane flying over the house”.
One might assume this statement was made by someone in Indonesia or Japan. However, the fact is that this came from someone in Sri Lanka. This statement came from D. M. Weerasekara, a resident of Kanawegala on the 26th night following an earth tremor felt in parts of the country.
Earth tremors are not common in Sri Lanka so this statement will grab the attention of the public. The Geological Survey and Mines Bureau (GSMB) said that during the space of one week the country experienced two earth tremors, of them one was experienced on the 20th of May and the other one on the 26th of May. On the 20th around 1.45 am the earth tremor was felt for about two minutes in Badulla, Nuwera Eliya, Maskeliya and Pidurugala. On the 26th of May at 9.52 pm an earth tremor was felt for about a minute in places including Nuwara Eliya, Hatton, Ampara, Matara, Jaffna and Colombo. The earth tremor was recorded at the Palakelle Seismology Centre, GSMB Chairman N. P. Wijeyananda said.
Residence of Padiyatalawa felt the effects of the second earth tremor which forced them to flee their homes out of fear. The tremor was felt at regular intervals in the area including in Serankada, Miriswatha, Kemalapitiya, Galmadu and Saranagama. Houses in Ridimalada, Kandakatiya were slightly damaged as a result of the force of the tremor.
During the first tremor, on the 20th of this month, the doors and windows of some houses were slightly damaged, according to residents of the area. Residents of Wawina experienced a similar tremor in the evening on April 11. However, the second tremor experienced last month was more powerful than the one experienced in April as several houses had been damaged on this occasion.
The Badulla disaster management center said that minutes before the first tremor, animals in the area had got disturbed. However, during the second tremor there was no noticeable disturbance among the animals. The disaster management centre said that they had now taken steps to keep the public informed when a tremor occurs in the future.
According to GSMB the earth tremor which occurred on the 20th of last month was recorded on the Richter scale at 3.3, while the tremor on the 26th was recorded at 3.4. However, these tremors were not felt in India or any other neighboring country.
Since an earth tremor is something unusual in Sri Lanka the public are now on alert following the twin earth tremors last month. The public have begun to fear an impending disaster as a result of the two tremors. Last Thursday a special discussion was held between the Disaster Management Center, the Minister in Charge (Mahinda Amaraweera), the Meteorological Department and other officials on the measures that need to be taken in the event of a major natural disaster. Meanwhile Wijeyananda said that the data collected from seismology centers in Sri Lanka following the last earth tremor was being used by specialists to conduct an investigation. Investigations will reveal if the tremor was natural or caused by instability in the earth’s crust.
Initial investigations have found the twin tremors had occurred near the central hills of the country. Dr Wijeyananda said that the data collected following the tremors were being compared in an attempt to identify the cause of the tremors.
Dr Wijeyananda said that similar tremors had been recorded in Sri Lanka’s past. During the Portuguese colonization of Sri Lanka in 1615 Colombo experienced a massive earth tremor which killed over 200 people. However, Wijeyananda said that Sri Lanka had not experienced a serious earth tremor since. He says this is because Sri Lanka is located away from active plate boundaries. Prof. Rohan Samarajeewa meanwhile explained that Sri Lanka is located on a plate and that may be the cause of the earth tremors. He also noted that people in high rise buildings feel the tremor even more and take precautions when such an incident occurs.
The world does not have the technology to predict when and where an earth tremor will occur and how big it may be. It is only after an earth tremor occurs that investigations are conducted and details regarding it are revealed. Wijeyananda said that there is no way of predicting future tremors.
In 2010 Sri Lanka experienced a mild earth tremor. Initially it was reported that the tremor was felt at a school, but later it was found the tremor was caused from an adjoining construction site. Later it was reported that a tremor was felt in the Hambantota and Tangalle area. However, subsequently it was revealed that the tremor was caused by a massive wall which had collapsed. This became the talk of the town in the media, especially since there was no recording of an earth tremor at the seismology center.
Meanwhile, on the 11th of April an 8.6 magnitude earthquake shook Sumatra, Indonesia which resulted in Sri Lanka feeling the aftershocks. Fears were then raised for a possible tsunami threat, but there was no such incident. In 2004 a 9.6 magnitude earthquake also in the same area resulted in Sri Lanka being struck by a devastating tsunami. The April 11 earthquake occurred 1700 kilometers away from the location where the 2004 earthquake had occurred. However, the fact that Sri Lanka did not suffer as a result of the April 11 earthquake shows how nature works. Scientifically one might expect things to happen but most often what you expect is not what occurs. Scientists say that the 2004 earthquake had, however, changed the geological makeup of the region. This could have resulted in the landscape also being affected.
The twin tremors experienced in Sri Lanka could raise fears of a massive disaster in future, but at what scale that disaster will be is something no one can predict. The public can only depend on what is revealed by the officials based on scientific and other forms of investigations.
Professor Rohan Samarajiva
An earth tremor is caused by the movement of two plates which is a natural occurrence. We mostly feel it when we are on high rise buildings or offices. But there is nothing special that causes such a tremor. This is the difference between science and general knowledge.
We felt the tremor caused by the earthquake off Indonesia in April. Such earthquakes will occur at least once a year.
The earthquake which occurred in 2004 was a massive one. Scientists say that could have resulted in some sort of instability in the ground. As predicted by some of these scientists, frequent earthquakes are occurring around the world.
Dr N. P. Wijeyananda – GSMB Chairman
Investigations are continuing over the earth tremors that have occurred in the country. We have been able to identify that the epicenters of these tremors were within Sri Lanka. We then identified the location of the epicenter. We are now looking at the impact the tremors had created on the geological landscape of the country. Several geologists are involved in the investigations.
Sri Lanka has rarely experienced a major natural disaster but we cannot say that in future such a disaster will not take place. Even the world cannot predict such a situation