Geez anon! Thanks for these.
Remember them. Did some for a snuff site in Texas, too, IIRC.
Anon, the STRAVA maps were used a couple of years ago to indicate human activity underground. Many of them are no longer available as it became obvious we were on to the tool.
STRAVA collects data from tracking tools like fit bits to show areas of intense human activity. When a path is show, but a satellite image proves there is no above-ground road or track, the assumption is that it's an underground facility.
Here's an article from the BBC:
https://www.bbc.com/news/technology-42853072