Fig. 9
![Fig. 9](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-018-0941-2/MediaObjects/40623_2018_941_Fig9_HTML.png)
Path number, coverage, and normalized relative path density of the phase-velocity measurements for four arbitrarily selected periods: a 1.5, b 2.5, c 3.5, and d 4.5Â s. Regions without path coverage are masked
Path number, coverage, and normalized relative path density of the phase-velocity measurements for four arbitrarily selected periods: a 1.5, b 2.5, c 3.5, and d 4.5Â s. Regions without path coverage are masked