The effect of confinement due to COVID-19 on seismic noise in Mexico

Abstract

Abstract. The world experienced the beginning of the COVID-19 pandemic by the end of 2019 to the beginning of 2020. Governments implemented strategies to contain it, most based on lockdowns. Mexico was no exception. The lockdown was initiated in March 2020, and with it, a reduction in the seismic noise level was witnessed by the seismic stations of the national and Valley of Mexico networks. Stations located in municipalities with more than 50 000 people usually experience larger seismic noise levels at frequencies between 1 and 5 Hz, associated with human activity. The largest noise levels are recorded in Mexico City, which has the largest population in the country. The largest drop was observed in Hermosillo, Sonora; however, it was also the city with the fastest return to activities, which seems to correlate with a quick increase in confirmed COVID-19 cases. Mexico initiated a traffic-light system to modulate the re-opening of economic activities for each state. Therefore, since 1 June, noise levels have generally reflected the colour of the state traffic light. Furthermore, the reduction in the noise level at seismic stations has allowed identification of smaller earthquakes without signal processing. Also, people in cities have perceived smaller or more distant quakes.

Variabilities in Urban Ambient Noise Before, During, and After Covid-19 Lockdown in the Peruvian Capital

“…A similar approach to highlighting the noise change at a particular frequency range can be seen in other related studies (e.g., Pandey et al, 2020;Poli et al, 2020;Somala, 2020;Yabe et al, 2020;Arroyo-Solórzano et al, 2021;Grecu et al, 2021;Kuponiyi and Kao, 2021;Nimiya et al, 2021;Pérez-Campos et al, 2021;Shen and Zhu, 2021). This is the frequency range where most of the day-to-day human activities occur like walking, traveling and other related cultural activities.…”

“…UAN is an amalgamation of ubiquitous signals generated by vibrations on the Earth's surface (Condori, 2021) other than natural sources such as earthquakes. Its sources can either be natural and/or anthropic, such as the wind, the circulation of vehicles, cars, trains, and airplanes; movement of people, small vibrations due to construction sites, industrial machinery, very small magnitude local earthquakes, earthquakes in distant places, even fluctuations in temperature and atmospheric pressure, and terrestrial and oceanic tides that transfer energy to the Earth's crust (Pérez-Campos et al, 2021). Based on the frequency content, the ambient noise can be divided into two broad categories as microseisms (< 1Hz) and microtremors (> 1Hz).…”

Visual Multimedia Intelligent Computing System for Seismic Performance of Bridge Structure Based on Object-Oriented Technology

“…Equations ( 16 ) and ( 17 ) indicate that the total input energy of the structure is all converted into the total energy of the KTH order single-degree-of-freedom software under the action of the KTH effective modal force [ 17 , 18 ].…”

Probing environmental and tectonic changes underneath Ciudad de México with the urban seismic field

“…The recorded urban noise is not stationary; a group of short-lived spectral peaks appears only in 2015. In 2020, the noise level drops at the onset of the Covid-19 pandemic (see Pérez-Campos et al, 2021). We will later on compare observed and modeled results from the two co-located sensors to assess the use of strong-motion stations for coda-wave monitoring (see Figure 1.…”