Fig. 10

Same as Fig. 6, but for the high-frequency (2–8 Hz) seismogram envelope at two elapsed times: (a) t = 20 s and (b) t = 170 s. In each frame, the left panel shows the RMS envelope amplitude, the center panel shows the envelope field reconstructed by the seismic gradiometry, and the right panel shows the slowness vectors estimated from the envelope. An MP4-formatted movie of the time-dependent wavefield is included in Additional file 5: Movie S5