The epicentre of the tremor was about 340 km South South West off Colombo and it occurred 10 km below the seabed, Director of the Centre of Earth Science Studies, Dr M G Kurien said.
The present indications was that there was no possibility of the tremor triggering tsunami waves, he told PTI.
People in parts of Thiruvananthapuram said they felt vibrations at around 4.30 PM. However no damage to property was reported.
Yesterday two mild tremors of 2.8 and 3.2 on the Richter scale occurred in parts of Idukki and Kottayam districts.