The May 21st, 2014 Bay of Bengal earthquake: implications for intraplate stress regime

摘要

The northeastern part of the Indian Ocean, i.e. the Bay of Bengal (BoB) is located near some of the most complicated tectonic zones on the Earth. An earthquake of magnitude similar to 6.0 occurred on 21 May 2014 near the coast of Odisha. Occasional moderate to large earthquakes in BoB highlight the need to study precise hypocentre locations, and focal mechanisms to understand the cause of intraplate seismicity in BoB. It is also important for seismic hazard and tsunami risk evaluation along the eastern coast of India. We present an analysis of the digital data of this earthquake recorded by regional and global networks of seismic stations. Our analysis of travel-times of P- and S-waves indicates that the epicentre of the earthquake is located between the Eighty Five East and Ninety East ridges. The focus of this earthquake was at a depth of 61 km, well below the lower boundary of the oceanic crust. The focal mechanism determined by modelling long period P- and SH-waveforms suggest an strike slip motion along a NW SE or NEE SWW-directed fault or fracture. We interpret that the upper part of the BoB lithosphere is abnormally strong and brittle.