AGU News:

Decrease of seismic noise level, after reduction of traffic due to the COVID‐19 pandemia, has been observed worldwide.

The possibility of using seismic noise as another proxy to estimate social isolation was tested with a station within Rio de Janeiro. Researchers used the isolation index measured from smart‐phone movement to calibrate the seismic noise levels and estimated an Isolation Seismic Index, ISI (% of the population at home), using the seismic noise energy.

Noise levels best correlate with isolation measures in the frequency range 4‐8Hz. Small differences between the smart‐phone and the ISI indexes are interpreted as differences in social activities and noise sources. All mobility indexes are proxies to the actual isolation.

Although ISI does not measure the number of people outside, it measures the number of noise sources (vehicles, trains, factories, etc.) and can be used as additional information to interpret anomalies in other proxies.

Plain Language Summary

A seismic station within Rio de Janeiro city showed a drastic reduction of seismic noise after isolation measures imposed by the state government and city council. Researchers show that the seismic noise level, due mainly to traffic, can be used as another proxy for the social isolation and can help interpret variations in the other indexes of people mobility.