Most people only hear about seismometers in the context of big earthquakes or volcanoes, but the sensitive instruments detect much gentler movements as well.
“They can pick up people moving, or public transportation,” said Yuri Tamama of the Class of 2022, who is analyzing data from campus seismometers as part of her internship with the Princeton Environmental Institute. “Before this project, I never expected some waves and wiggles on a seismogram to show so much information about the environment.”
In recent months, seismometers have seen a sharp decline in the level of background noise as human activity has been curtailed in response to COVID-19. The seismograms recorded in the basement of Guyot Hall reveal the decline in local seismic noise, first after the end of on-campus instruction on March 13, and then a more dramatic decrease after Governor Murphy’s stay-at-home order on March 21.
“The noise level had been high and then just went off a cliff,” said Dr. Jessica Irving, a visiting research collaborator in geosciences who is one of Tamama’s advisers. “There was a small change in noise levels over Spring Break, but when we were told, ‘Don't come to campus, it's not good for safety,’ people just stopped.”
Similar patterns have appeared in other data sets, from traffic cameras to cellphone movements, but seismicity can provide useful information without compromising privacy.
Tamama’s project this summer is comparing the seismic record from spring 2020 with that of previous years, working with Irving and Frederik Simons, a professor of geosciences. She is still compiling the data, but she expects the difference will be stark. She is also looking forward to seeing what other patterns emerge. “The abundance of knowledge that can be gleaned from seismology is so interesting,” she said.
Irving is part of an international collaboration tracking seismic background data — and its implications for coronavirus response — around the globe. “I've never published a paper that involves human behavior before,” she said with a laugh. (Her usual subject is the Earth’s deep interior, using seismic data to study the core and mantle.) “This is a very different flavor of science, but it's the same data, it's just it's telling a different story,” said Irving, who is now a senior lecturer at the University of Bristol.
“It seems like ‘Team Princeton’ is really working hard to try and reduce transmission, and so that's what we see right now in the data,” Irving said. “Maybe the virus would have been worse in New Jersey, if not for the behavior that we saw.”