Digana tremors to continue?

Mahaweli Authority launches study

By Sarah Hannan

The tremors and other seismic activities that have been reported since August in the Victoria Reservoir area will continue to take place, as the earth undergoes weathering changes, Geological Survey and Mines Bureau (GSMB) Chairman Anura Walpola said.

The Sunday Morning contacted Walpola on Friday (20) following the seismic activity recorded on Wednesday (18) at 9.27 a.m. of a magnitude of 2.0 on the Richter scale.

However, Walpola assured that the tremor had not caused any threat to the residents or had any impact on the Victoria Dam or the reservoir.

“This area has been experiencing such seismic activity periodically, with the most recent one being between 29 August and 2 September, at different intervals. The tremors take place when the pressure that gets trapped within the earth’s crust is released, and the area is mainly composed of dolomite marble and charnockite rocks. The marble bands that form the valley will have pressure relief areas that are underlain by charnockite rocks which are resistant to weathering and with time, it releases the pressure, either making a cracking noise or seismic activity that causes tremors,” Walpola told The Sunday Morning.

The Mahaweli Authority has requested experts from the Civil Engineering Department of the University of Peradeniya and deployed a team from the Mahaweli Authority to conduct further studies over these seismic activities to understand the long-term effect it could pose to the stability of the reservoir and the dam structure.

“A report was already submitted to us regarding the previous tremors that took place and the geologists and seismologists are closely monitoring the weathering changes that are taking place in the area as of recently. According to their findings, these are minor incidents and completely normal occurrences. There is no major impact on the reservoir or the residents of the area at present,” Mahaweli Authority Director General Engineer B.A. Sunil Perera told The Sunday Morning.

The GSMB stated that they are continuously monitoring the seismometers that are installed within the Victoria Dam complex as well, like other weather instruments under observation. Studies are also carried out to understand the reactions of the area’s soil and mineral deposits to the weather changes.

Walpola also noted that in other countries, they generally release the pressure that builds between two rock layers through artificial methods, and Sri Lanka does not have the technology to do the same at the moment.