Focal mechanism and radiated energy determination of the M_(S)7.9 earthquake in Myanmar on March 28,2025OA

On March 28,2025,an M_(S)7.9 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 Wphase 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.