Seismometer noise includes storms, 'footquakes' from soccer matches (2011)
phys.org
phys.org
https://ethz.ch/en/news-and-events/eth-news/news/2020/07/loc...
edit: I wonder if you could establish a correlation between countries that went into lockdown but still had high levels of basal seismic activity and total number of corona infection cases? As in people not respecting lockdown guidelines or countries implementing partial/selective lockdown having higher infection rates.
It really shouldn't be that surprising to anyone who's ever attended a soccer match, you can practically feel thousands of tons of concrete flexing.
[1] E.g. in Italian, from a few years back: seismometers record fans shouting "the champions" in sync with Champion's League anthem, and this was only 40k people. https://twitter.com/Eurosport_IT/status/781503844920520704
That is a lot of energy, but still at the bottom of the Richter scale. According to Wikipedia: "Microearthquakes, not felt, or felt rarely. Recorded by seismographs.", occurring several million times per year.
Seismographs are just very sensitive.
If you walk up to one and jump nearby, you'll see a fairly significant signal being recorded. They're particularly sensitive, I've seen them picking up trucks driving a km or so away. They do know how to ignore this though.
For a nice country-wide seismograph display, there is: https://www.geonet.org.nz/earthquake/drums though (fortunately) it's looking a bit boring right now.