• GSMB Seismologist Nilmini Thaldena emphasises need for development projects in populated, urban areas to consider qualitative aspects of high-rise building constructions to mitigate possible impacts of earth tremors  

The string of earth tremors that were felt in various parts of the Island and in the immediate sea area during the past few months was alarming. Although none of these tremors caused considerable damage to properties or lives, the number of tremors, which is on the rise with another one being reported last week in Monaragala, has shaken the public’s sense of safety.

However, the relevant authorities are of the opinion that the recent earth tremors do not pose a considerable risk to the country. While that assurance may not be adequate in the face of a series of earth tremors, the authorities stress that their conclusion is a scientific one based on the available data. Although more data would have helped reach better conclusions, they are confident about the country’s ability to identify the intensity of earth tremors.

This situation was explained by the Geological Survey and Mines Bureau (GSMB) Seismologist Nilmini Thaldena in an interview with The Daily Morning. She noted that while monitoring, investigating and when possible, dealing with disasters such as earth tremors, which are viewed solely as the authorities’ responsibility, there are steps that the public too can take to minimise the possible impacts of earth tremors, especially on buildings. She added that as now Sri Lanka is paying unprecedented attention to earth tremors, taking seriously the quality related aspects of buildings, especially in populated areas such as Colombo, should be a main concern in development projects. 

Below are the excerpts from the interview:

We refer to what Sri Lanka experienced during the past few months as ‘earth tremors’. Is there a difference between an earth tremor and what we generally refer to as an earthquake?

Earth tremors are less intense compared to earthquakes. But, what happens in both the cases is essentially a seismic movement.

How does an earth tremor occur, and what triggers it?

The earth’s crust consists of several layers called plates. These plates move to different directions, usually by several centimetres a year. In this process, some plates move away from each other while some get closer. This process involves a certain friction, and the energy that gets generated within the earth due to that friction getting released is what happens in an earthquake. This process involves a lot of other factors that change the nature and intensity of an earthquake.

In response to the recent spate of earth tremors, the authorities including the GSMB said that there is nothing for the public to be alarmed about? What is the rationale behind it?

The manner in which earth tremors occur varies from location to location. We can forecast, based on a geological background, which areas are more susceptible to earth tremors, the likelihood of such and the intensity of the same. When it comes to Sri Lanka and its location, we don’t expect a significant risk. That is why we say that there is no reason to be alarmed about, and that is a statement that we make on the basis of the knowledge and information that we have at the moment. 

Have you reached any predictions based on the investigations that are being conducted into the recent earth tremors?

No. The database that we have does not cover a long history, its data dates back only to 2012. When we take into account the details of that database, the information that is available to us and the recent earth tremors, we are not yet in a position to make any predictions as to the reasons that may have led to these earth tremors and what areas could be most at risk because we don’t have adequate data. However, constant monitoring activities in this regard are underway.

What sort of precautions could the public, especially those who live in the areas where earth tremors have been reported, take?

Despite the level of risk, it is advisable that we be ready to face any disaster or risk. There were reports that vibrations were reported in Colombo recently. In such a context, it is important to take measures to ensure that the high-rises and other major projects in such areas are implemented in a manner that enables such projects to withstand earth tremors. Ensuring the quality of such projects is crucial not only for these types of disasters, but in other forms of disasters as well.

Do we have adequate resources and other frameworks necessary to monitor and investigate earth tremor related matters, and in what ways could these activities improve?

At present, we have adequate resources to monitor and identify earth tremors. But, with more resources, we could improve the accuracy of the information that we gather. For example, even though we have machines set up to measure earth vibrations, which help us monitor earth tremor related incidents, it would be more helpful if we could install more such machines. As the GSMB, we are currently holding discussions about getting more resources. However, it should also be noted that the present situation, in which we pay more attention to earth tremors, is a relatively new one. Earlier, this was not a major topic, which did not call for such increased attention. It is when an issue arises that we have to seek a solution. In fact, it is after 2004 that we started paying attention to earthquakes. We have not reached a level where we have to complain about not having sufficient funds. These activities are moving forward gradually. If the situation exacerbates, we will have to obtain more resources, including the necessary machines. But, at present, we are continuing the basic functions properly. 

Various earth related activities, especially mining, are taking place in Sri Lanka, which has very limited space. Could these activities be playing a certain role in the recent string of earth tremors that have been reported?

A vibration within the earth could be a result of both an artificial or human caused reason or the aforementioned natural phenomenon which involves plates within the earth. Although such human led activities could lead to certain issues, in Sri Lanka, at present, they are not taking place at a scale that could lead to massive disasters. 

What do you think about aspects of this field that need to change or improve in the Sri Lankan context?

We reach conclusions based on the knowledge about the earth that we have already acquired. However, if we improved and expanded our studies of the earth, we would be able to reach better conclusions. More data also helps us compare our situation with the global situation too. The more data that we can get our hands on, the more accurate the conclusions we can reach. For example, with more tools, we can go beyond general conclusions such as Colombo felt a vibration and instead gauge the intensity of such vibrations and the level of risk that they pose.