"During lockdowns and other measures to control the spread of the novel coronavirus there was as much as a 50% drop globally in the seismic vibrations humans normally generate, according to new research." Why does that matter? "Human seismic noise can drown out signals from earthquakes, volcanic eruptions and other geological hazards and natural sources. The "quiet period" of 2020 may help to improve warning systems by offering an opportunity to separate natural sounds from those generated by human activity." Using data from 268 seismic stations in 117 countries, researchers measured the effects of lockdown on high-frequency (4-14 Hz) Seismic Ambient Noise (hiFSAN), finding a "near global reduction in noise, commencing in China in late Jan 2020, then followed by Europe and the rest of the world" from March to April 2020.