Written by Pavani Hapuarachchi
30 Nov, 2020 | 6:59 pm
COLOMBO (News 1st): The magnitude of the tremor reported from Aluthwatta, Ambakotte, and Digana areas on Sunday night (Nov. 29) was recorded at below 2.0 on the Ritcher Scale, the Geological Survey & Mines Bureau said.
The tremor was also recorded as a very minor tremor on the Ritcher Scale at the Victoria reservoir, and as minor tremors at the Pallekele and Mahakandarawa seismic centres, the Bureau further noted.
From 29th August to-date (Nov. 30), such minor tremors were reported five times, from Gurudeniya, Rajawella, Thalathu-Oya, Haragama, and Anuragama in Kandy.
According to the Geological Survey and Mines Bureau, the tremors were recorded far away from an active plate margin and free of large scale seismic activities.
The Committee of Experts appointed by the Minister of Environment to probe the tremors released its report including observations and recommendations recently.
Geologists suspect that rock bursts inside relatively weak limestone or reservoir induced/triggered earthquake surrounding the Victoria dam as possible causes for the tremors, the report noted.
The report has pointed out five possible causes for the tremors, as follows:
01 – Dolamite excavation
02 – Use of detonators for construction purposes
03 – Natural tectonic behaviour
04 – Natural Rock Bursts
05 – Rapid water level changes in the Victoria reservoir
The Committee report concludes that further investigations be conducted into the matter.
While observing that cracks were reported on several houses in the area, the report concludes the observed level of seismicity is not harmful to the Victoria dam.
When inquired on the matter, Senior Lecturer at the Department of Geology of the Science Faculty at the University of Peradeniya – Prof. Athula Senaratne, said the continuous occurrence of tremors is not a good sign, adding it was high-time to conduct an in-depth study into the tremors.
“The recurrence of tremors means there is a prominent geological phenomenon in the respective area that needs to be looked into. Such small tremors are at times followed by greater tremors and therefore, informed decisions should be made, Prof. Athula Senaratne told News 1st on Monday (Nov. 30).
Following the tremors recorded last night (Nov. 29), the area residents of Aluthwatta, Ambakotte, and Digana areas speaking News 1st said, they were worried about their safety.
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