An improved method for seismic moment tensor inversion of acoustic emissions through assessment of sensor coupling and sensitivity to incidence angle

•We propose ultrasonic calibration technique of acoustic emission sensors.•Procedure useful when specimen and acoustic emission sensors are inside loading cell.•Acoustic emission waveforms corrected for coupling quality and incidence angle.•Full moment tensor inversion performed for Bentheim and Vosges sandstones.•Ultrasonic calibration compared with hybrid moment tensor technique.