On the Source Mechanism and Radiated Energy Determination of the 2025 MS7.9 Myanmar Earthquake

Abstract

An MS7.9 earthquake was recorded in the Himalayan Myanmar arc tectonic belt at the boundary between the Indian and Eurasian plates (2025 MS7.9 Myanmar earthquake) on March 28, 2025. In this paper, broadband waveform data offered by the Global Seismographic Network is utilized to invert the centroid moment tensor and focal mechanism of this earthquake through the application of the W-phase method and the P-wave first-motion polarity inversion method. In line with the results obtained, the radiated energy of the earthquake is determined using the far-field point source model, the global attenuation model, and the energy flux density method. The energy-to-moment ratio, apparent stress, stress drop, and radiated energy enhancement factor are calculated through the combination of the determined seismic moment. From the findings, it can be seen that (1) The earthquake is identified as a high-angle strike-slip event, with the focal mechanism solution showing a nodal plane I having a strike of 358°, a dip of 70°, and a rake of -175°, and a nodal plane II having a strike of 266°, a dip of 85°, and a rake of -20°. The seismic moment is calculated to be 4.94×1020N·m, corresponding to a moment magnitude of 7.7. The centroid location is determined to be at 21.21°N, 95.92°E, with a depth of 35.0 km and a centroid time of 35 s; (2) The radiated seismic energy is found to be 2.6×1016 J, corresponding to an energy magnitude of 8.0, which exceeds the moment magnitude; (3) The energy-to-moment ratio is 5.3×10-5, with the apparent stress being 1.58 MPa, the stress drop being 6.79 MPa, and the radiated energy enhancement factor that describes the complexity of the fault rupture being113; (4) In accordance with the results of this study, the Myanmar earthquake can be considered as a strike-slip event characterized by a high fault dip angle and a relatively high energy release efficiency. In contrast with earthquakes of the same magnitude, such earthquakes are found to possess a greater potential for destruction to local buildings and infrastructure, and are more likely to cause severe disasters.

Keywords: Myanmar MS7.9 earthquake, source mechanism, seismic radiated energy, W-phase inversion, energy flux density method