Focal mechanism and radiated energy determination of the M_S7.9 earthquake in Myanmar on March 28, 2025

On March 28, 2025, an M_S7.9 earthquake occurred in the Himalayan–Myanmar Arc at the junction of the Indian Plate and the Eurasian Plate. Utilizing broadband waveform data provided by the Global Seismographic Network, this study adopted the W-phase method and the P-wave first-motion polarity method to invert the centroid-moment-tensor and fault plane solutions of this earthquake. Additionally, the far-field point source model, global attenuation model, and energy flux density method were used to determine the radiated energy of this earthquake. The energy–moment ratio, apparent stress, stress drop, and radiated energy enhancement factor were also calculated based on the measured seismic moment. The main findings are as follows: (1) this event was a strike-slip earthquake with steeply dipping faults. The focal mechanism solution yielded two nodal planes: Plane I (strike 358°, dip 70°, rake −175°) and Plane II (strike 266°, dip 85°, rake −20°). The seismic moment of 4.94 × 10²⁰ N·m corresponds to a moment magnitude of 7.7. The centroid was located at 21.21°N and 95.92°E and a depth of 35.0 km. The centroid time was 35 s. (2) The radiated seismic energy was 2.6 × 10¹⁶ J, which was converted to an energy magnitude of 8.0, higher than the moment magnitude. (3) The energy–moment ratio was 5.3 × 10⁻⁵, apparent stress was 1.58 MPa, stress drop was 6.79 MPa, and radiated energy enhancement factor describing the complexity of fault rupture was calculated as 113. (4) In summary, the Myanmar earthquake is a strike-slip earthquake, characterized by steeply dipping faults and highly efficient energy release. Compared with earthquakes of the same magnitude, such earthquakes have a greater destructive power on local buildings and infrastructure, increasing the likelihood of severe disasters.