Seismic Silence of Canadian Cities

On 11 March 2020, the COVID-19 was declared a global pandemic by the World Health Organization (WHO). By 20 March 2020, all provinces and territories in Canada were under their first lockdown and the Canada-US border was closed to check the spread of COVID-19. (See Lockdown Timeline for Canada)

The closure of borders, businesses, restaurants, schools, and all non-essential travel and services lead to a reduction in human movements. This reduction in human movements was picked up by the seismic stations across all nine Canadian cities in six provinces considered for the study.

All Canadian Cities Went Seismically Silent During COVID-19 Lockdown

All Canadian cities went seismically silent a week after the World Health Organization declared COVID-19 a global pandemic. The seismic vibrations associated with human and cultural noises decreased between 12% to 55% during the first lockdown period (March 2020 – May 2020). The biggest drop of over 30% was observed in Montreal (Quebec), Calgary (Alberta), and Ottawa (Ontario). In Whitehorse (Yukon) and Halifax (Nova Scotia), the drop was between 20% and 30%. While in Toronto (Ontario), Quebec City (Quebec), Vancouver (BC), and Victoria (BC) the drop was between 10% and 20%.

See the graph below for an overview of the seismic silence because of the reduction in human movements. The brighter the pixels the more seismically active the city during that period.

City Specific Results of Seismic Silences

The detailed results of the decrease in seismic vibrations during the COVID-19 lockdown period have been presented city wise. Information has been provided on when each of these cities declared a public health emergency and went for a lockdown and when the lockdown started to ease.

Validation of Results from Ground and Space-based Measurements

In Toronto, the findings from sub-surface measurements of seismic vibrations were validated by the ground measurements. I did in Toronto to measure the traffic levels, pollution levels (PM 2.5 count) and street sounds during the lockdown period. The traffic levels fell by 50% while the street sounds went down by 30% during this period pointing to reduction in transportation and outdoor human activities.

Limitations

  • Seismic stations are very sensitive instruments. They are purposely built outside the urban areas so that they are isolated from city noises. As seismic stations chosen for this project were at different distances (5 km – 80 km) from the city centers, they were not equally sensitive to changes in human activities.
  • Lockdowns were enforced in all the cities included in this project. However, the definition of which services were considered essential and remained open during the lockdown varied.
  • All Canadian cities had a hard start date of the first lockdown (around 18 March 2020). However the end date of the first lockdown varied. Some cities extended the lockdown while others opened up with some restrictions.

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