With Covid-19, a Seismic Quiet Like No Other

The shock waves of civilization travel through rocky ground and, at times, ricochet around the globe, as geologists know from decades of listening for earthquakes with sensitive seismometers. The human pulses come from heavy traffic, football games, rock concerts, fireworks, subways, mine explosions, rock drilling, factories, jackhammers, industrial blasts and other activities. In 2001, vibrations from the collapse of the World Trade Center registered in five states. Seismometers even picked up the impacts of the two airplanes.

Now, a team of 76 scientists from more than two dozen countries reports that lockdowns from the Covid-19 pandemic led to a drop of up to 50 percent in the global din tied to humans. The main quieting, from March through May, was compared with levels in previous months and years.

“The length and quiescence of this period represents the longest and most coherent global seismic noise reduction in recorded history,” the scientists reported on Thursday in the journal Science. The quieting, they added, resulted from social distancing, industrial shutdowns and drops in travel and tourism. The overall decline far exceeded the kind typically observed on weekends and holidays.

Devices for measuring earthquakes go back at least to the early part of the 18th century, when pendulums were used to display ground motions. In 1895 an Irish engineer, John Milne, established on the Isle of Wight a modern seismometer center that quickly grew into the world’s first global network, with 30 overseas branches. By 1957, an international group of seismologists listed 600 stations. The devices can pick up vibrations not only from earthquakes and human activities but from hurricanes and the crashing of ocean waves on shorelines, as well as the impacts of rocky intruders from outer space.