Fig. 10

a Enlargement of the right side of the top plot of Fig. 3. JBE and MVLP waveforms can be seen. b Dominant periods of the waveforms in a. The dispersion of the surface waves is clear, and in the range of periods from 17.5 to 16.5 s is visible in the waveform (marked by red line). The red arrow indicates 09:58:38 UTC. c Notch filter output of the waveform with the notch in the period of 15.6 s and a bandwidth of 1 s. The black arrow indicates 09:59:09 UTC