Fig. 10
![Fig. 10](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-021-01408-1/MediaObjects/40623_2021_1408_Fig10_HTML.png)
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