ECONOMYNEXT – Sri Lanka’s geologists say they are pursuing two lines of inquiry in trying to explain a recent increase in observed earthquake activity in the Indian Ocean Island involving Indo-Australian plate and internal geological formations.
Sri Lanka is generally considered to have been free of major earthquakes or volcanoes for thousands of years. Its major geological activity involving separating lowlands and the hill country is believed to have occurred about 600 to 800 million years ago.
Authorities Lanka had documented 16 small tremors and 18 in 2021. In 2022 there were 5 reported seismic events and in 2023 so far 9, Acting Director General of Sri Lanka’s Geological Survey and Mines Bureau Ajith Prema said.
The boundary forming the Indo-Australia plate and Sunda sub-plate is where the active Indonesian earthquakes take place generating frequent tsunamis.
Scientists believe that that the India and Australia plates which are virtually fused may have started to separate again about three million years ago. The Himalayas are a result of the Indian plate moving northwards very slowly and colliding with the Eurasian plate.
The active zone in Indonesia is located about 1,600 kilometres away and the Himalayas about 2,000 kilometres away.
“The Indian and Australia plate boundary is located about 900 to 1,000 kilometres away from Sri Lanka which is closer,” Prema said.
“These activities take thousands or millions of years. The probability of any major earthquakes happening is very small.”
A second line of inquiry that geologists are pursuing is on the internal geological formations of the island.
Scientists have identified three main areas in the island involving the Vanni complex, the Highland complex and the Vijayan complex.
Along the boundary of the Vijayan complex which runs from the Eastern coast to Hambantota and the Highland complex activity like hot spring (geothermal energy) is seen.
Sone of the earthquakes reported, for example in Buttala falls along the boundaries of the two complexes.
Geologist Nalin de Silva says it is difficult to say still whether there is any actual increase in activity due to the lack of past data.
There was reason to believe that seismic activity had gone unreported in the past, because people may have not have paid much attention to such phenomena unlike now, officials said.
“There is now greater public awareness,” de Silva said. “The measuring equipment has also got more sensitive. There is equipment in Sri Lanka, the region and globally which are much more sensitive.”
The GSMB is constructing maps, collecting data and analyzing the information, he said.
The GSMB is also in talks with Sri Lanka’s survey department to install equipment along the boundaries of the geological complex to check if there is any measurable movements, de Silva said.