Geologists believe that the recent tremors that occurred in Sri Lanka are showing characteristics of a new tectonic boundary creation approximately 900-1,000 km away to the south of Sri Lanka. 

Speaking at a recent press conference, Geological Survey and Mines Bureau (GSMB) Acting Director General Janaka Ajith Prema reiterated that the GSMB had collaborated with international agencies to carry out further observations and monitoring exercises to determine the possible impacts this would have on Sri Lanka’s seismic activities.

He added: “There have been 16 earthquakes in 2020, 18 earthquakes in 2021, five earthquakes in 2022, and nine earthquakes in 2023 (January-April).”      

A 1995 paper authored by Orman et al titled ‘Distribution of shortening between the Indian and Australian Plates in the central Indian Ocean’ published in Earth and Planetary Science Letters revealed the existence of a new plate boundary in the central Indian Ocean that creates a separation of the Indo-Australian Plate into the Indian Plate and Australian Plate. 

This plate boundary is said to be located 400-500 km from the southern shores of Sri Lanka and geologists suggest that Sri Lanka’s seismic activity levels should be classified as a moderate earthquake-prone area given the proximity to the new plate boundary.

In an article authored by University of Peradeniya Department of Geology Prof. C.B. Dissanayake in 2005 titled ‘A new plate boundary near Sri Lanka: Implication for future geohazards,’ the new plate boundary is said to meet the subduction zone of the Java-Sumatra Trench at a triple junction (closer to the epicentre of the 26 December 2004 earthquake in the region). 

This proximity to a region that is hyperactive with earthquakes will therefore have a significant impact on the new plate boundary.

The article further revealed that scientists from Melbourne University led by Professor Michael Sandiford had discovered that the Indo-Australian Plate, after the split, had been experiencing considerable stress from the neighbouring plates of Indonesia and Asia. 

Therefore, the energy generated from the connection points between plates at Sumatra and Java is transferred back to the Indian and Australian Plates, causing immense tectonic stress. This kind of stress is known to produce earthquakes up to 7.0 on the Richter scale every 30 years.

Meanwhile, former Senior Professor of Geology at the University of Peradeniya Athula Senaratne noted: “Observing data collected over a 30-year period from across the world, there is an increased tendency for earthquakes to occur during the months of November through April. 

“Our recent observation regarding the tremor that occurred in April approximately 26 km off the coast of Hambantota at a 4.4 magnitude on the Richter scale was that it could have been an aftershock of the major earthquake that occurred in Indonesia. When a major earthquake takes place on an adjacent tectonic plate, it is possible for some of that stress to pass to the neighbouring plates as well,” he explained. 

Given the increase in earth tremors taking place in various parts of Sri Lanka, the Disaster Management Centre, through its district-level Disaster Management Units, is conducting awareness sessions for communities living in and around multi-storey buildings, private companies, Government institutions, and schools regarding the steps to follow during an earthquake/earth tremor.

Safety measures to follow during an earthquake

According to the US Centers for Disease Control and Prevention, the following three basic steps can keep you and your loved ones safe during an earthquake:

• Drop down onto your hands and knees before the earthquake knocks you down. This position protects you from falling but allows you to still move if necessary.
• Cover your head and neck (and your entire body if possible) underneath a sturdy table or desk. If there is no shelter nearby, get down near an interior wall or next to low-lying furniture that won’t fall on you, and cover your head and neck with your arms and hands.
• Hold on to your shelter (or to your head and neck) until the shaking stops. Be prepared to move with your shelter if the shaking shifts it around.
• Stay inside if you are inside and outside if you are outside:
• Move away from buildings, utility wires, sinkholes, and fuel and gas lines. The greatest danger from falling debris is just outside doorways and close to the outer walls of buildings.
• Go to an open area away from trees, telephone poles, and buildings. Once in the open, get down low and stay there until the shaking stops.
• The area near the outside walls of a building is the most dangerous place to be. Windows, facades, and architectural details are often the first parts of the building to collapse. Stay away from this danger zone.

Source: Centers for Disease Control and Prevention