Source characteristics of the upper mantle 21 May, 2014 Bay of Bengal earthquake of ${{\varvec{M}}}_{\!{{\varvec{w}}}}$5.9

Abstract

We measure source parameters for the 21 May, 2014 Bay of Bengal earthquake through inversion modeling of S-wave displacement spectra from radial–transverse–vertical (RTZ) components recorded at ten broadband stations in the eastern Indian shield. The average source parameters are estimated using estimates from seven near stations (within epicentral distances ${\le }500\,\hbox {km}$). The average seismic moment and source radius are determined to be $1.0{\times }10^{18}\,\hbox {N-m}$ and 829 m, respectively, while average stress drop is found to be 76.5 MPa. The mean corner frequency and moment magnitude are calculated to be $1.6\pm 0.1$ and $5.9\pm 0.2$ Hz, respectively. We also estimated mean radiated energy and apparent stress, which are found to be $6.1{\times }10^{13}$ joules and 1.8 MPa, respectively. We observe that mean $E_{s}/M_{o}$ estimate of $5.5{\times }10^{-5}$ is found to be larger than the global average for oceanic strike-slip events. This observation along with large stress drop and apparent stress estimates explains the observed remarkably felt intensity data of the 2014 event. The full waveform moment tensor inversion of the band-passed (0.03–0.12 Hz) broadband displacement data suggests the best fit for the multiple point sources on a plane located at 65 km depth, with a moment magnitude 6.4, and a focal mechanism with strike $318^{\mathrm{o}}$, dip $87^{\mathrm{o}}$, and rake $34^{\mathrm{o}}$.