The 24 August 2021 Mw 5.1 earthquake, 320 km northeast of Chennai, India: brittle rupture of a fault line

On 24 August 2021 at 12:35:50 IST, an undersea earthquake of magnitude M_w 5.1 on the Richter scale occurred at a depth of around 10 km and shook some parts of the southeast coast of India (source: USGS). The epicentre of the quake lay in the Bay of Bengal (BoB) at 14.440°N lat. and 82.991°E long., about 296 km southeast of Kakinada, Andhra Pradesh and 320 km northeast of Chennai (Figure 1). A few coastal parts of Tamil Nadu and Andhra Pradesh felt mild tremors, but there was noreported destruction, tsunami warning and aftershocks. Although the eastern BoB has witnessed a few earthquakes in the historical past (see figure 1 of Krishna et al.1), the western BoB has remained relatively stable. The last activity was noticed more than a century ago on 19 May 1918 at a location of 15.9°N, 83.7°E (Figure 1). Inthe recent past, on 21 May 2014, the eastern BoB had witnessed a 6.0 magnitude earthquake at 18.3°N, 87.9°E. These quakes are situated in the far interior away from active seismic zones such as divergent/convergent/transform plate boundaries, and also from diffusive plate boundary in the Indian Ocean.